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Chapter:, , Ten, , Light: Reflection and Refraction, , S, , s, a, D, hiv, , BASED, , 6. A point object is placed at a distance of 20 cm, from a convex mirror of focal length 20 cm., 1. When light falls on a smooth polished surface,, The image will form at:, most of it, (a) at infinity, (a) is reflected in the same direction, , (b) at focus, (b) is reflected in different directions, (c) at the pole, (c) is scattered , , (d) behind the mirror, (d) is refracted into the second medium, Ans. (d) behind the mirror, Ans. (a) is reflected in the same direction, 7. Focal length of a concave mirror is, 2. Image formed by reflection from a plane, (a) negative, mirror is, (b) positive, (a) real and inverted, (c) depends on the position of object, , (b) virtual and erect, (d) depends on the position of image, (c) real and erect, Ans. (a) negative, , (d) virtual and inverted, 8. If the power of a lens is – 2 D, what is its focal, Ans. (b) virtual and erect, length?, 3. If an incident ray passes through the focus,, (a), +50 cm, (b) –100 cm, the reflected ray will, (c) –50 cm, (d) +100 cm, (a) pass through the pole , Ans. (c) –50 cm, (b) be parallel to the principal axis, 9. A spherical mirror and a spherical lens each, (c) retrace its path , have a focal length of – 10 cm. The mirror and, (d) pass through the centre of curvature, the lens are likely to be, Ans. (b) be parallel to the principal axis, , (a) both concave , 4. Magnifying power of a concave lens is, (b) both convex, (a) always > 1, , (c) the mirror is concave and the lens is convex, , (b) always < 1, (d), the mirror is convex and the lens is concave, (c) always = 1, Ans. (a) both concave, , (d) can have any value, 10. If the magnification produced by a lens has a, Ans. (b) always < 1, negative value, the image will be, 5. The image formed by a convex lens can be, (a) virtual and inverted, (a) virtual and magnified , (b) virtual and erect, (b) virtual and diminished, (c) real and erect, (c) virtual and of same size, (d) real and inverted, (d) virtual image is not formed, Ans. (b) virtual and erect, Ans. (a) virtual and magnified, C-29, ,  Multiple Choice Questions (MCQs), , COMPETENCY, , Competency Based Questions

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Light: Reflection and Refraction, , C-30, , , , Shiv Das Chapterwise Question Bank (Science X), , 11. When the object is placed between f and 2f of, a convex lens, the image formed is, (a) at f, , (b) at 2f, , (c) beyond 2f, , (d) between O and f, Ans. (c) beyond 2f, 12. Which mirror can produce a virtual, erect and, magnified image of an object?, (a) Concave mirror, , (b) Convex mirror, (c) Plane mirror, (d) Both concave and convex mirrors, Ans. (a) Concave mirror, , 13. If the image is formed in front of the mirror,, then the image distance will be, (a) positive or negative depending on the size, of the object, (b) neither positive nor negative, (c) positive, (d) negative, Ans. (d) negative, 14. A ray of light is travelling from a rarer medium, to a denser medium. While entering the denser, medium at the point of incidence, it, , (a) goes straight into the second medium, (b) bends towards the normal, (c) bends away from the normal, (d) does not enter at all, Ans. (b) bends towards the normal, , 15. A student does the experiment on tracing the path of a ray of light passing through a rectangular, glass slab for different angles of incidence. He can get a correct measure of the angle of incidence, and the angle of emergence by following the labelling indicated in figure:, , , (a) I, , (b) II, , Ans. (d) IV, ,  Assertion-Reason Questions, , s, a, D, v, i, h, S, (c) III , , In the following question, a statement of Assertion, (A) is followed by a statement of Reason (R)., Answer these questions by selecting appropriate, option given below:, (a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of, Assertion (A)., (b) Both Assertion (A) and Reason (R) are true but, Reason (R) is not the correct explanation of, Assertion (A), (c) Assertion (A) is true but Reason (R) is false., (d) Assertion (A) is false but Reason (R) is true., 1. Assertion (A): Higher is the refractive index of, a medium or denser the medium, lesser if the, velocity of light in that medium., , Reason (R): Refractive index is inversely, proportional to velocity., Ans. (a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of, Assertion (A)., , (d) IV, , According to Snell’s law:, , sin i n2 c / v2 v1, = =, =, sin r n1 c / v1 v2, , , ,  n1 v1 = n2v2, This shows that higher is the refractive index of a, , medium or denser the medium, lesser is the velocity, of light in that medium., 2. Assertion (A): For observing traffic at back, the, driver mirror is convex mirror., , Reason (R): A convex mirror has much large, field of view than a plane mirror., Ans. (c) Assertion (A) is true but Reason (R) is false., The image of real object may be real in case of, concave mirror., 3. Assertion (A): If the rays are diverging after, emerging from a lens; the lens must be concave., , Reason (R): The convex lens can give diverging, rays., Ans. (d) Assertion (A) is false but Reason (R) is true., If the rays cross focal point of convex lens, they, become diverging.

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Competency Based Questions, , 10. Assertion (A): A virtual image cannot be, photographed., , Reason (R): Only real objects are photographed., Ans. (c) Assertion (A) is true but Reason (R) is false., An image in a plane mirror is virtual and it can be, photographed., ,  Case Study Based Questions, 1. Read the following and answer any four, questions from (i) to (v):, Rear view mirror is a device that allows the, driver to see rear ward. It usually finds its place, at the top of windscreen in side the cabin. This, device is one of the most basic but essential, safety devices in the vehicle. It provides, assistance to the driver during overtaking,, parking in reverse gear etc. Generally, vehicles, also have a pair of mirrors attached to the body, from outside. They are popular as ‘side mirrors’, or Outer Rear View Mirrors (ORVM) which, serve the same purpose. Almost all modern, cars mount their side mirrors on the doorsnormally at A-pillar rather than the wings (the, portion of the body above the wheel well)., , s, a, D, hiv, , S, , C-31, , , , BASED, , (i) A real image of an object is to be obtained., The mirror required for this purpose is:, , (a) convex mirror , , (b) concave mirror, (c) plane mirror , , (d) either convex or concave mirror, Ans. (b) concave mirror, (ii) A boy is standing in front of and close to a, special mirror. He finds the image of his head, bigger than normal, the middle part of his, body of the same size, and his legs smaller, than normal. The special mirror is made up of, three types of mirrors in the following order, from top downwards:, , (a) Convex, Plane, Concave, , (b) Plane, Convex, Concave, (c) Concave, Plane, Convex, , (d) Convex, Concave, Plane, Ans. (c) Concave, Plane, Convex, As, plane mirror will produce an image of the same, size. A concave mirror will produce a magnified, image and a convex mirror will produce a diminished, image., (iii) A convex mirror is used:, , (a) by a dentist. , , (b) for shaving., , COMPETENCY, , 4. Assertion (A): The height of an object is always, considered positive., , Reason (R): An object is always placed above, the principal axis in the upward direction., Ans. (a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of, Assertion (A)., 5. Assertion (A): The image formed by a concave, mirror is certainly real if the object is virtual., , Reason: The image formed by a concave mirror, is certainly virtual if the object is real., Ans. (c) Assertion (A) is true but Reason (R) is false., The image of real object may be real in case of, concave mirror, 6. Assertion (A): A convex mirror is used as a, driver’s mirror., , Reason (R): Because convex mirror’s field of, view is large and images formed are virtual,, erect and diminished., Ans. (a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of, Assertion (A)., 7. Assertion (A): It is not possible to see a virtual, image by eye., , Reason (R): The rays that seem to emanate, from a virtual image do not in fact emanates, from the image., Ans. (d) Assertion (A) is false but Reason (R) is true., 8. Assertion (A): Propagation of light through an, optical fiber is due to total internal reflection, taking place at the core-clade interface., , Reason (R): Refractive index of the material of, the core of the optical fiber is greater than of, air., Ans. (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation, of Assertion (A)., Optical fiber communication is based on the, phenomenon of total internal reflection at core-clade, interface. The refractive index of the material of, the cladding, hence, light sinking at core-cladding, interface gets totally internal reflected. The light, undergoes and reaches the other end of the fiber., 9. Assertion (A): Large concave mirrors are used, to concentrate sunlight to produce heat in solar, cookers., , Reason (R): Concave mirror converges the, light rays falling on it to a point., Ans. (a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of, Assertion (A)., Concave mirror converges the light rays falling, on it to a point. So large concave mirrors are used, to concentrate sunlight to produce heat in solar, cookers., , 

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Light: Reflection and Refraction, , C-32, , , , Shiv Das Chapterwise Question Bank (Science X), , (c) as a rear view mirror in vehicles., , (d) as a light reflector for obtaining a parallel, beam of light., Ans. (c) as a rear view mirror in vehicles., (iv) Linear magnification (m) produced by a rear, view mirror fitted in vehicles:, , (a) is equal to one , , (b) is less than one, (c) is more than one , , (d) can be more or less than one depending on, the position of object., Ans. (b) is less than one, (v) A concave mirror cannot be used as:, , (a) a magnifying mirror , , (b) a torch reflector, (c) a dentist’s mirror , , (d) a rear view mirror, Ans. (d) a rear view mirror, Because a concave mirror produces inverted images, (upside down images) of distant objects., 2. Read the following and answer any four, questions from (i) to (v):, , An Overhead Projector (OHP), like a film or, slide projector; uses light to project an enlarged, image on a screen. In the OHP, the source of, the image is a page-sized sheet of transparent, plastic film (also known as foils) with the image, to be projected either printed or hand-written/, drawn. These are placed on the glass surface of, the projector, which has a light source below, it and a projecting mirror and lens assembly, above it as shown in the figure., , , (b) The image when passed through the lens, was inverted and then it gets reflected on, the mirror to be obtained on the screen., (c) The screen used automatically makes the, image erect and real. , , (d) Both (b) and (c), Ans. (b) The image when passed through the lens, was inverted and then it gets reflected, on the mirror to be obtained on the, screen., (iii) Why is concave mirror used and not convex, mirror in this projector?, , (a) because concave mirror can give real image., , (b) because convex mirror can give real image., (c) because concave mirror cannot give real, image., , (d) because convex mirror cannot give virtual, image., Ans. (a) because concave mirror can give real image., (iv) If the radius of curvature of concave mirror is , 12 cm. Then, the focal length will be:, , (a) 12 cm, , (b) 6 cm, (c) –24 cm, , (d) –6 cm, Ans. (d) –6 cm, As we know, f = R/2 = 12/2 = 6 cm, But the sign of focal length of concave mirror is, negative. Therefore f = -6 cm, , s, a, D, v, i, h, S, , Plane, mirror, Focus, lense, , Image, Screen, Object, , , , Concave, mirror, , (i) Based on the diagram shown, what kind of, lens is used to make the overhead projector., , (a) concave lenses, , (b) convex lenses, (c) bifocal lenses, , (d) flat lenses, Ans. (b) convex lenses, (ii) The image obtained will be erect and real., How?, , (a) The image when passed through the lens, was erect and was directly obtained on the, screen. , , (v) The power of a convex lens is __________ and, that of a concave lens is __________ ., , (a) positive, negative, , (b) positive, positive, (c) negative, positive , , (d) negative, negative, Ans. (a) positive, negative, 3. Read the following and answer any four, questions from (i) to (v):, , A mirror is a surface that reflects a clear image., Images can be of two types: Real image and, virtual image. An image that can be formed on, the screen is known as a real image and the, one which cannot be formed on the screen is, known as a virtual image. These images are, formed when light falls on a mirror from the, object and is reflected back by the mirror on, the screen., One useful tool that is frequently used to depict, this idea is known as a ray diagram. A ray, diagram is a diagram that traces the path that, light takes in order for a person to view a point

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Competency Based Questions, , C-33, , 4. Read the following and answer any four, questions from (i) to (v):, , Aditya and his friend Manoj placed a candle, flame in front of a convex lens at various, distances from it and obtained the image of the, candle flame on a white screen., He noted down the position of the candle,, screen and the lens as under, Position of candle = 20 cm, Position of convex lens = 50 cm, Position of the screen = 80 cm, B, A, , Convex lens, , A’, B’, , s, a, D, hiv, , S, , A, , O, , B 2F, , F, , C, , 1 1 1,    1  1   1 , f v u, f 30  30 , 1, 1, 1, 2,    , f 30 30 30, , , Now,, , F B’ 2F, A’, , (v) An object is placed at focus of a concave, mirror, image will be formed at:, , (a) focus, (b) between F and C, (c) beyond C, , (d) at infinity, Ans. (d) at infinity, A, , Y, , C, X, , B, , F, , E, , D, ,  f = 15 cm, (iii) Where will the image be formed if he shifts, the candle towards the lens at a position of 35, cm?, , (a) At focus, , (b) Between focus and pole, (c) At infinity, , (d) Between F2 and F1, Ans. (c) At infinity, When the candle is shifted towards the lens at a, position of 35 cm., Object distance, u = –(50 – 35) = –15 cm, , , 1 1 1,  , f v u, , BASED, , (i) What is the position of the image formed, from the convex lens?, , (a) 80 cm, , (b) 50 cm, (c) 30 cm, , (d) 60 cm, Ans. (c) 30 cm, Image distance, v, = Position of screen – Position of convex lens,  v = 80 – 50 cm = 30 cm, (ii) What is the focal length of the convex lens?, , (a) 30 cm, , (b) 15 cm, (c) –16 cm, , (d) 16 cm, Ans. (b) 15 cm, Object distance, u, = Position of convex lens – Position of candle, u = (50 – 20) = –30 cm, , COMPETENCY, , on the image of an object. On the diagram, rays, (lines with arrows) are drawn for the incident, ray and the reflected ray., A ray diagram used arrow type lines to, represent the incident ray and the reflected, ray. It also helps to trace the direction in which, light travels., (i) Convex mirror always forms, an image:, , (a) Virtual, erect and enlarged., , (b) Virtual, inverted and enlarged., (c) Virtual, erect and diminished., , (d) Real, erect and diminished., Ans. (c) Virtual, erect and diminished., (ii) A convex lens forms the image of sun at:, , (a) C, (b) focus, (c) pole, , (d) between focus and pole, Ans. (b) focus , (iii) A concave lens can form a real and inverted, image, when:, , (a) Object is placed at 2F., (b) Object is placed beyond 2F., (c) Object is placed between f and 2F., , (d) It can never form a real and inverted image., Ans. (d) It can never form a real and inverted image., (iv) An object is placed beyond 2F, in front of a, convex lens, image will be formed:, , (a) between F and 2F, (b) at focus, (c) at the centre of curvature, , (d) between focus and Optical centre., Ans. (a) between F and 2F, , 

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C-34, , , , Shiv Das Chapterwise Question Bank (Science X), , 1 1 1, , 15 v 15, 1, , , =0, v, , , , , ,  v =  (Infinite), , Light: Reflection and Refraction, , When object is placed at focus, image is formed at, infinity., , lenses are more powerful. So to see far away,, she needed a big powerful lens. Unfortunately,, she realized that a big lens is very heavy. Heavy, lenses are hard to make and difficult to hold in, the right place. Also since the light is passing, through the lens, the surface of the lens has, to be extremely smooth. Any flaws in the lens, will change the image. It would be like looking, through a dirty window., , (iv) Which of the following statement describes, the best about the nature of the image formed, s, Telescope Diagram, ge, Len, if Aditya shifts the candle towards the lens to , Ima, 36 cm?, L1, , (a) The nature of the image formed will be, virtual, inverted and magnified., e, ec, , (b) The nature of the image formed will be, pi, ye e, E, L2, virtual, erect and magnified., ey, To, (c) The nature of the image formed will be , virtual, erect and diminished., (i) Based on the diagram shown, what kind, , (d) The nature of the image formed will be, of lenses would Sumati need to make the, real, inverted and diminished., telescope?, Ans. (b) The nature of the image formed will be, , (a) Concave lenses, virtual, erect and magnified., , (b) Convex lenses, , (c) Bifocal lenses, (v) Manoj noted following observations at, , (d) Flat lenses, different positions of candle from the lens., According to Aditya one set of observations Ans. (b) Convex lenses, (ii) If the powers of the lenses L1 and L2 are in the, is incorrect. Find out if Aditya is right or not., ratio of 4 : 1, what would be the ratio of the, , (a) Distance of the flame from the lens = 60 cm;, focal length of L1 and L2?, Distance of the screen from the lens = 20 cm, , (a) 4 : 1, (b) 1 : 4, , (b) Distance of the flame from the lens = 45 cm;, (c) 2 : 1, (d) 1 : 1, Distance of the screen from the lens = 22.5 cm, Ans. (b) 1 : 4, (c) Distance of the flame from the lens = 30 cm;, We have,, Distance of the screen from the lens = 30 cm, 1, 1, , (d) Distance of the flame from the lens = 10 cm;, P1 =, and P2 =, f1, f2, Distance of the screen from the lens = 15 cm, 1, Ans. (d) Distance of the flame from the lens = 10 cm;, P1 4, f, 4, 1, Distance of the screen from the lens = 15 cm, = , =, Given., 1 1, P2 1, The observation (d) is incorrect. For this observation, f2, v = 15, i.e., the image is at the focus and the object, f1 1, =, must be formed at infinity and not 10 cm., Hence,, or 1: 4, , s, a, D, v, i, h, S, , 5. Read the following and answer any four, questions from (i) to (v):, Sumati wanted to see the stars of the night, sky. She knows that she needs a telescope to, see those distant stars. She finds out that the, telescopes, which are made of lenses, are called, refracting telescopes and the ones which are, made of mirrors are called reflecting telescopes., So she decided to make a refracting telescope., She bought two lenses, L1 and L2, out of which, L1 was bigger and L2 was smaller. The larger, lens gathers and bends the light, while the, smaller lens magnifies the image. Big, thick, , f2, , 4, , (iii) What is the formula for magnification, obtained with a lens?, , (a) Ratio of height of image to height of, object., , (b) Double the focal length., (c) Inverse, of, the, radius, of, curvature., , (d) Inverse of the object distance., Ans. (a) Ratio of height of image to height of object., Magnification (m) =, , h' v, =, h u

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Competency Based Questions, , We know, m =, ,  3 =, , 24, u, , C-35, , (v) Sumati bought not-so-thick, lenses, for, the telescope and polished, them., What, advantages, if any, would she have with her, choice of lenses?, , (a) She will not have any advantage as even, thicker lenses would give clearer images., , (b) Thicker lenses would have made the, telescope easier to handle., (c) Not-so-thick lenses would not make the, telescope very heavy and they will also, allow considerable amount of light to pass, through them., , (d) Not-so-thick lenses will give her more, magnification., Ans. (c) Not-so-thick lenses would not make the, telescope very heavy and they will also, allow considerable amount of light to pass, through them., ----------, , v, u, , Hence, u = 8 cm, , S, , s, a, D, hiv, , COMPETENCY, , (iv) Sumati did some preliminary experiment, with the lenses and found out that the, magnification of the eyepiece (L2) is 3. If in, her experiment with L2 she found an image at, 24 cm from the lens, at what distance did she, put the object?, , (a) 72 cm, (b) 12 cm, (c) 8 cm, (d) 6 cm, Ans. (c) 8 cm, Given. m = 3, v = 24, u = ?, , , , BASED

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C-36, , , , Shiv Das Chapterwise Question Bank (Science X), , The Human Eye and the Colourful World, , Chapter:, , The Human Eye and, the Colourful World, , Eleven, , Competency Based Questions,  Multiple Choice Questions (MCQs), 1. The least distance of distinct vision for a, normal eye is, (a) infinity, (b) 25 cm, (c) 2.5 cm, (d) 25 m, Ans. (b) 25 cm, 2. A person cannot see distinctly objects kept, beyond 2 m. This defect can be corrected by, using a lens of power, (a) +0.5 D, (b) –0.5 D, (c) +0.2 D, (d) –0.2 D, Ans. (b) –0.5 D, 3. The defect of vision in which a person cannot, see the distant objects clearly but can see, nearby objects clearly is called, (a) myopia, (b) hypermetropia, (c) presbyopia, (d) bifocal eye, Ans. (a) myopia, 4. The splitting of white light into different, colours on passing through a prism is called, (a) reflection, (b) refraction, (c) dispersion, (d) deviation, Ans. (c) dispersion, 5. At noon, the Sun appears white as, (a) blue colour is scattered the most, (b) red colour is scattered the most, (c) light is least scattered, (d) all the colours of the white light are, scattered away, Ans. (c) light is least scattered, 6. Twinkling of stars is due to, (a) reflection of light by clouds, (b) scattering of light by dust particles, , (c) dispersion of light by water drops, (d) atmospheric refraction of starlight, Ans. (d) atmospheric refraction of starlight, 7. When white light enters a glass prism from, air, the angle of deviation is least for, (a) blue light, (c) yellow light, (c) violet light, (d) red light, Ans. (d) red light, 8. When white light enters a glass prism from, air, the angle of deviation is maximum for, (a) blue light, (b) yellow light, (c) red light, (d) violet light, Ans. (c) red light, 9. The amount of light entering the eye can be, controlled by the, (a) iris, (b) pupil, (c) cornea, (d) ciliary muscles, Ans. (b) pupil, 10. What type of image is formed by the eye lens, on the retina?, (a) Real and erect, , (b) Virtual and inverted, (c) Real and inverted, , (d) Virtual and erect, Ans. (c) Real and inverted, 11. The medical condition in which the lens of, the eye of a person becomes progressively, cloudy resulting in blurred vision is called, (a) myopia, , (b) hypermetropia, (c) presbyopia, , (d) cataract, Ans. (d) cataract, , s, a, D, v, i, h, S, , C-36

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Competency Based Questions, , In the following question, a statement of Assertion, (A) is followed by a statement of Reason (R)., Answer these questions by selecting appropriate, option given below:, (a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of, Assertion (A)., (b) Both Assertion (A) and Reason (R) are true but, Reason (R) is not the correct explanation of, Assertion (A), (c) Assertion (A) is true but Reason (R) is false., (d) Assertion (A) is false but Reason (R) is true., 1. Assertion (A): The sky appear dark instead of, blue to an astronaut., , Reason (R): There is no atmosphere containing, air in space to scatter sunlight., Ans. (a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of, Assertion (A)., , As there is no atmosphere in space and hence light, does not scatter into its constituents colours that, is why the sky appears dark instead of blue to an, astronaut in space., , BASED, , 2. Assertion (A): A Hypermetropic eye is, corrected by using a convex lens of suitable, focal length., , Reason (R): It is caused by shortening of the, eyeball size., Ans. (a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of, Assertion (A)., When a convex lens of suitable power is placed in, front of the hypermetropic eye then the diverging, rays of light coming from the nearby object are first, converged by this convex lens., Due to this, the convex lens forms a virtual, image of the nearby object at a point near to the, hypermetropic eye. Then the hypermetropic eye can, easily focus the image formed by convex lens on the, retina., 3. Assertion (A): The splitting up of white light, into seven colours on passing through a, transparent medium like a glass prism is called, scattering of light., , Reason (R): The angle of refraction (or angle, of bending) of lights of different colours is, different when passing through the glass prism, because different colours travel at different, speeds., Ans. (d) Assertion (A) is false but Reason (R) is true., The splitting up of white light into seven colours on, passing through a transparent medium like a glass, prism is called dispersion of light., 4. Assertion (A): Rainbow is caused by dispersion, of sunlight by tiny water droplets present in, the atmosphere., , Reason (R): A rainbow is always formed in the, direction opposite to that of the Sun., Ans. (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation, of Assertion (A)., 5. Assertion (A): The change in focal length of an, eye lens is caused by the action of the ciliary, muscles., , Reason (R): The power of accommodation of, the eye increases with ageing., Ans. (c) Assertion (A) is true but Reason (R) is false., The power of accommodation of the eye decreases, with ageing., 6. Assertion (A): Newton showed that the, seven coloured lights of the spectrum can be, recombined to give back white light., , Reason (R): When a beam of white light is, passed through a glass prism, a band of seven, colours is formed on a white screen., Ans. (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation, of Assertion (A)., , s, a, D, hiv, , S, ,  Assertion-Reason Questions, , C-37, , COMPETENCY, , 12. The defect of the eye in which the eye-ball, becomes too long is, (a) myopia, , (b) hypermetropia, (c) presbyopia, , (d) cataract, Ans. (a) myopia, 13. The defect of vision in which the image of, nearby objects is formed behind the retina, is, (a) myopia, , (b) short-sightedness, (c) hypermetropia, , (d) presbyopia, Ans. (c) hypermetropia, 14. Which of the following is a natural phenomenon which is caused by the dispersion of, sunlight in the sky?, , (a) Twinkling of stars, (b) Stars seem higher than they actually are, (c) Advanced sunrise and delayed sunset, (d) Rainbow, Ans. (d) Rainbow, 15. Name the scientist who was the first to use a, glass prism to obtain the spectrum of sunlight., (a) Isaac Newton, , (b) Einstein, (c) Kepler, (d) Hans Christian Oersted, Ans. (a) Isaac Newton, , 

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The Human Eye and the Colourful World, , C-38, , , , Shiv Das Chapterwise Question Bank (Science X), , 7. Assertion (A): The scattering of longer, wavelengths of light increases as the size of the, particles increases., , Reason (R): Large particle scatter lights of all, wavelengths equally well., Ans. (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation, of Assertion (A)., 8. Assertion (A): The twinkling of stars is due, to the fact that refractive index of the earth’s, atmosphere fluctuates., , Reason (R): When light propagates from one, medium to another its direction of propagation, changes., Ans. (a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of, Assertion (A)., , The continuously changing atmosphere is able to, cause variation in the light coming from a pointsized star appears to be twinkling., 9. Assertion (A): There is no dispersion of light, refracted through a rectangular glass slab., , Reason (R): Dispersion of light is the, phenomenon of splitting of a beam of white, light into its constituents colours., Ans. (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation, of Assertion (A)., , After refraction at two parallel faces of a glass slab,, a ray of light emerges in a direction parallel to the, direction of incidence of white light on the slab. As, rays of all colours emerge in same direction, hence, there is no dispersion only lateral displacement, takes place., 10. Assertion (A): Higher the refractive index, of the prism material, lower is the angle of, deviation., , Reason (R): The angle of deviation is directly, proportion to the angle of prism., Ans. (d) Assertion (A) is false but Reason (R) is true., , Higher the refractive index of the prism material,, greater is the angle of deviation., , When white light consisting of seven colors, falls on a transparent medium (glass prism),, each color in it is refracted (or deviated) by, a different angle, with the result that seven, colors are spread out to form a spectrum., , , c, ati, , m, hro, lyc, Po, White Light, , Monochromatic Light, Red, Orange, Yellow, Green, Blue, Indigo, Violet, Glass prism, , ht, Lig, , (i) A beam of white light falls on a glass prism., The colour of light which undergoes the least, bending on passing through the glass prism, is:, , (a) violet, (b) red, (c) green, (d) blue, Ans. (b) red, (ii) The colour of white light which suffers the, maximum bending (or maximum refraction), on passing through a glass prism is:, , (a) yellow, (b) orange, (c) red, (d) violet, Ans. (d) violet, (iii) Which of the following colour of white light, is least deviated by the prism?, , (a) green, (b) violet, (c) indigo, (d) yellow, Ans. (d) yellow, (iv) The colour of white light which is deviated, the maximum on passing through the glass, prism is:, , (a) blue, (b) indigo, (c) red, (d) orange, Ans. (b) indigo, (v) The splitting up of white light into seven, colours on passing through a glass prism is, called:, , (a) refraction, (b) deflection, (c) dispersion, (d) scattering, Ans. (c) dispersion, , s, a, D, v, i, h, S, ,  Case Study Based Questions, 1. Read the following and answer any four, questions from (i) to (v):, Dispersion is the splitting up of white light into, seven colours on passing through a transparent, medium like a glass prism. When a white light, beam is passed through a prism, a band of, seven colors are formed is known as spectrum, of white light as shown in given figure., , 2. Read the following and answer any four, questions from (i) to (v):, The twinkling of a star is due to atmospheric, refraction of starlight. The starlight on entering, the earth’s atmosphere, undergoes refraction, continuously before it reaches the earth. The, atmospheric refraction occurs in a medium

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Competency Based Questions, , Star, , Apparent, star position, , Ray path, , (c) Refraction,, dispersion, and, internal, reflection., , (d) Dispersion, scattering and total internal, reflection., Ans. (c) Refraction,, dispersion, and, internal, reflection., (v) Which of the following statements is, correct regarding the propagation of light, of different colours of white light in, air?, , (a) Red light moves with the fastest speed., , (b) Blue light moves faster than green light., (c) All the colours of the white light move, with the same speed., , (d) Yellow light moves with the mean speed as, that of the red and the violet light., Ans. (c) All the colours of the white light move with, the same speed., , S, , (i) The stars seem higher than they actually are, due to:, , (a) Reflection of light, (b) Refraction of light, (c) Scattering of light , , (d) Inference of light, Ans. (b) Refraction of light, (ii) Stars appear to twinkle because of:, , (a) Atmospheric refraction, , (b) Movement of air, (c) Both (a) and (b) , , (d) None of these, Ans. (c) Both (a) and (b), (iii) At noon, the Sun appears white as:, , (a) Light is least scattered., , (b) All the colours of the white light are, scattered away., (c) Blue colour is scattered the most., , (d) Red colour is scattered the most., Ans. (a) Light is least scattered., (iv) Which of the following phenomenon of light, is involved in the formation of rainbow?, , (a) Reflection, refraction and dispersion, , (b) Refraction, dispersion and total internal, reflection., , , , i + e =  + A, A, , i, , B, , Q, , P, r, , r’, , e, , C, , (i) The angle between the two refracting surfaces, of a prism is called ____________., (a) angle of prism, (b) angle of incidence, (c) angle of deviation, , (d) angle of emergence, Ans. (a) angle of prism, , BASED, , 3. Read the following and answer any four, questions from (i) to (v):, A prism is a transparent refracting medium, bounded by two plane surfaces inclined to, each other at a certain angle. The refraction, of light through a prism, follows the laws, of refraction. In the prism refraction takes, place on its refracting surface it means when, the light enters the prism and when the light, leaves the prism. The refraction through a, prism is shown. Here A is the angle of prism,, i is the angle of incidence of the face AB and, e is the angle of emergence at other face AC., The incident ray suffers a deviation or bending, through an angle  due to the refraction, through prism. This angle is called angle of, deviation as shown in figure., , s, a, D, hiv, , Refracting Index, increasing, , , , C-39, , COMPETENCY, , of gradually changing refractive index. Since, the atmosphere bends starlight towards the, normal, the apparent position of the star is, slightly different from its actual position. The, star appears slightly higher than its actual, position when viewed near the horizon., Further this apparent position of the star is, not stationary, but keeps on changing slightly,, since the physical conditions of the earth’s, atmosphere are not stationary. Since the stars, are very distant they are approximate pointsized source of light. As the path of rays of light, coming from the star goes on varying slightly,, the apparent position of the star fluctuates, and the amount of starlight entering the eye, flickers the stars sometimes appear brighter, and at some other time, fainter, which is the, twinkling effect., , 

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The Human Eye and the Colourful World, , C-40, , , , Shiv Das Chapterwise Question Bank (Science X), , (ii) The angle between the incident ray and the, emergent ray is called ____________., , (a) angle of emergence, (b) angle of deviation, (c) angle of incidence, , (d) none of these, Ans. (b) angle of deviation, (iii) When a ray is refracted through a prism, then, , (a) i = , , (b) i = e + , (c)  = e, , (d) i > r, Ans. (d) i > r, (iv) The angle of deviation depends on, , (a) refraction index of prism, (b) angle of incidence, (c) both (a) and (b), , (d) none of these, Ans. (c) both (a) and (b), (v) The rectangular surfaces of a prism are know, as:, , (a) reflecting surfaces, (b) dispersing surfaces, (c) refracting surfaces, , (d) none of these, Ans. (c) refracting surfaces, , (ii) At the time of sunrise and sunset, the light, from sun has to travel through ____________., , (a) longest distance of atmosphere, , (b) shortest distance of atmosphere, (c) both (a) and (b) , , (d) can’t say, Ans. (a) longest distance of atmosphere, (iii) The colour of sky appears blue, it is due to, the, , (a) refraction of light through the atmosphere, , (b) dispersion of light by air molecules, (c) scattering of light by air molecules , , (d) all of these, Ans. (c) scattering of light by air molecules, (iv) At the time of sunrise and sunset, , (a) Blue colour scattered and red colour reaches, our eye., , (b) Red colour scattered and blue colour, reaches our eye., (c) Green and blue scattered and orange, reaches our eye. , , (d) None of these., Ans. (a) Blue colour scattered and red colour reaches, our eye., (v) The danger signs made red in colour, because, , (a) the red light can be seen from farthest, distance, , (b) the scattering of red light is least, (c) both (a) and (b), , (d) none of these, Ans. (c) both (a) and (b), , s, a, D, v, i, h, S, , 4. Read the following and answer any four, questions from (i) to (v):, , The spreading of light by the air molecules is, called scattering of light. The light having least, wavelength scatters more. The sun appears, red at sunrise and sunset, appearance of blue, sky it is due to the scattering of light. The, colour of the scattered light depends on the, size of particles. The smaller the molecules in, the atmosphere scatter smaller wavelengths, of light. The amount of scattering of light, depends on the wavelength of light. When, light from sun enters the earth’s atmosphere,, it gets scattered by the dust particles and air, molecules present in the atmosphere. The path, of sunlight entering in the dark room through, a fine hole is seen because of scattering of the, sun light by the dust parties present in its path, inside the room., (i) To an astronaut in a spaceship the colour of, earth appears, , (a) red, (b) blue, (c) white , (d) black, Ans. (b) blue, , 5. Read the following and answer any four, questions from (i) to (v):, Atmosphere refraction is the phenomenon of, bending of light on passing through earth’s, atmosphere. As we move above the surface of, earth, density of air goes on decreasing. Local, conditions like temperature etc. also affect, the optical density of earth’s atmosphere., On account of refraction, stars seen appear, higher than they actual are; advanced sunrise;, delayed sunset, oval appearance of the sun at, sunrise and sunset; stars twinkle, planets do, not., (i) , Due to atmospheric refraction, apparent, length of the day, , (a) increases, , (b) decreases, (c) remains the same , , (d) all of these, Ans. (a) increases

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Competency Based Questions, , (iv) Twinkling of stars and non-twinkling of, planets is accounted for by, , (a) Scattering of light, , (b) dispersion of light, (c) atmospheric refraction, , (d) none of these, Ans. (c) atmospheric refraction, (v) In absence of atmosphere, the colour of sky, appears, , (a) blue, , (b) black, (c) red, , (d) yellow, Ans. (b) black, , ----------, , s, a, D, hiv, , S, , C-41, , COMPETENCY, , (ii) Apparent position of the star appears raised, due to, , (a) atmospheric refraction, (b) scattering of light, (c) both (a) and (b) , , (d) none of these, Ans. (a) atmospheric refraction, (iii) The sun appears oval shaped or flattened due, to, , (a) dispersion, , (b) scattering, (c) atmospheric refraction, , (d) cannot say, Ans. (c) atmospheric refraction, , , , BASED