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PHYSICS PROBLEMS, 1. The electrostatic force on a metal sphere of charge 0.4µC due to another identical metal, sphere of charge -0.8µC in air is 0.2N. Find the distance between the same two spheres, and also find the force between the same two spheres when they are brought in to, contact and then replaced in their initial positions., 2. Two tiny spheres each of mass 10-5 kg are suspended from a point by threads each 0.5 m, long. They are equally charged and repel each other to a distance of 0.28m. what is the, charge on each ? g = 10m.s-2, 3. A sphere carrying a charge of +20μC is placed at a certain distance from another, identical sphere carrying a charge of -80μC . The two spheres are brought in contact,, separated and kept in their original positions. Compare the forces between them before, and after they are in contact?, 4. Two identical metallic spheres, having equal opposite charges are placed at a distance of, 0.50m apart in air. After bringing them in contact with each other, they are again placed, at the same distance apart. Now the force of repulsion between them is 0.108 N., Calculate the final charge on each of them., 5. A pendulum bob of mass 80 mg and carrying a charge of 20 nc is at rest in a horizontal, uniform electric field of strength 20,000 NC-1. Find the tension in the thread of the, pendulum and the angle it makes with the vertical., 6. Four point charges qA = 2µc; qB = -5µc; qC =2µc; qD = -5µA are located at the corners of a, square ABCD of side 10 cm. What is the force on a charge of 1 µc placed at the centre of, the square?, 7. Two fixed point charges +4μC and +1μC are separated by 30cm in air. Find the, position between them at which the resultant electric field is zero., 8. ABC is a right angled triangle such that AB=3m, BC=4m and, = 900. Charges of, 9nC and -16nC are placed at the corners A and C respectively. Calculate the resultant, electric intensity and direction at point B., 9. Two charges 10μC and 20μC are placed at the corners of the hypotenuse BC of a right, angled triangle ABC of sides AB=3m and AC=4m. Calculate the resultant electric field, at the corner A., 10. Two charges 2μ C and 3 μ C are placed at two corners of an equilateral triangle of side, 20cm in free space. Calculate the magnitude of resultant electric intensity at the third, corner of the triangle. If an α- particle is placed at the third corner what is the force, acting on it?, 11. Four charge Q, 2Q, 3Q and 4Q are placed at the corner of a square ABCD of side 0.1m, . If the intensity of electric field at the center of the square is 5.1103 NC 1 , find Q ., 12. Two charges 5x10-8C and -3x10-8C are located 16cm apart. At what point on the line, joining the two charges is the electric potential zero? Take the potential at infinity to be, zero., 13. Two point charges qA=3µC and qB= -3µC are located 20cm apart in vacuum. What is, the electric field at the midpoint O of the line AB joining the two charges?If a negative

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test charge of magnitude 1.5×10-9C is placed at this point , what is the force, experienced by the test charge?, 14. Three charges each equal to +4nC are placed at the three corners of a square of side 2cm., Find the electric field at the fourth corner. [March 2018], 15. ABCD is a square of side 2m. Charges of q A = 5 µC, qB = 10 µC, qC = 5 µC are placed at, corners A, B and C respectively. What is the work done in transferring a charge of, 5µC from D to the point of intersection of the diagonals?, 16. A point charge of 25µc is situated at a point O. A and B are points 0 .05m and 0.15m, away from this charge. Calculate the amount of work done to move an electron from B, to A., 17. Two charges 30nC and -20nC are located 15 cm apart. At what points on the line, joining the two charges is the electric potential zero? Take the potential at infinity to be, zero. [July 2014], 18. Two point charges +1 nC and - 4 nC are 1m apart in air. Find the positions along the, line joining the two charges at which resultant potential is zero. [March 2015], 19. Charges 2 μ C, 4 μ C and 6 μ C are placed at the three corners A, B and C of a square, ABCD of side x metre. Find what charge must be placed at the fourth corner so that net, potential at the centre of the square becomes zero. [July 2016], 20. ABCD is a square of side 2m. Point charges of 5nC, 10nC and -5nC are placed at corners, A, B, C respectively. Calculate the work done in transferring a charge of 5 μ C from D to, the point of intersection of diagonals. [June 2015], 21. In a parallel plate capacitor with air between the plates, each plate has an area of 6 × 10−3, m2 and the distance between the plates is 3 mm. Calculate the capacitance of the, capacitor. If this capacitor is connected to a 100 V supply, what is the charge on each, plate of the capacitor? [March 2014], 22. In a parallel plate capacitor with air between the plates, each plate has an area of 8 × 10 −3, m2 and the distance between the plates is 2 mm. Calculate the capacitance of the, capacitor. If this capacitor is connected to a 50 V supply, what is the charge on each plate, of the capacitor? (Absolute permittivity of free space = 8.85 X 10-12 Fm-1) [June 2017], 23. The plates of a parallel plate capacitor have an area of 100cm2 each and are separated by, 3mm. The capacitor is charged by connecting it to a 400V supply. Calculate (a) the, electrostatic energy stored in the capacitor, (b) if a dielectric of constant 2.5 is introduced, between the plates of the capacitor, then find electrostatic energy stored and also change, in the energy stored. (J-18), 24. Energy stored in a system consisting of two capacitors in series and connected across, 4kV line is 8J. When the same two capacitors are in parallel across the same line, energy, stored is 36J. Find the capacitance of the capacitors., 25. When two capacitors are connected in series and connected across 1kV, the energy, stored in the system is 2J. The same capacitors if connected in parallel across to same, line, the energy stored are 9J. Find the capacitance of capacitors.

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26. Two capacitors of capacitances 5 µF and 10 µF are charged to 16 V and 13 V respectively., What is the common potential when they are connected in parallel with (a)The plates, having similar charges together and (b)The plates having opposite charges together, 27. A 4 μ F capacitor is charged by a 200V supply. It is then disconnected from the supply, and is connected to another uncharged 2 μ F capacitor. How much electrostatic energy, of first capacitor is dissipated in the form of heat and electromagnetic radiation?, 28.Two capacitors of capacitances 3 and 5 are charged to potentials of 300V and 500V, respectively. They are connected by a wire. Calculate the common potential, charge on, each capacitor and the loss of energy., 29. Two capacitors of capacity 5 μ F & 10 μ F are charged to 16V and 13V, respectively. What is the common potential when they are connected in parallel?, Calculate charge on each capacitor., 30. Two capacitors of capacitance 600pF and 900pF are connected in series across a 200V, supply. Calculate (i) the effective capacitance of the combination, (ii) the p.d. across each, capacitor and (iii) the total charge stored in the system., 31. Two resistors of resistances 3Ω and 6Ω are connected in parallel with a battery of emf 6V, and internal resistance 1Ω.Calculate the main current through the circuit and current, through 3Ω and 6Ω., 32. (a) Three resistors 2 Ω,3 Ω , and 4 Ω are combined in series. What is the total resistance, of the combination?, (b) If the combination is connected to a battery of emf 10 V and negligible internal, resistance, obtain the potential drop across each resistor. [March 2016], 33. (a) Three resistors 4Ω, 6Ω and 8 Ω are combined in parallel. What is the total resistance, of the combination? (b) If the combination is connected to a battery of emf 25 V and, negligible internal resistance, determine the current through each resistor, and the total, current drawn from the battery. [June 2017], 34. Two resistors of resistance 12Ω and 6 Ω are connected in parallel to a battery of 12V. (a), Calculate the equivalent resistance of the network. (b) Obtain the current in 12 Ω and, 6Ω resistors. [July 2014], 35. A battery of internal resistance 3Ω is connected to 20Ω resistor and potential difference, across the resistor is 10V. If another resistor of 30Ω is connected in series with the first, resistor and battery is again connected to the combination, calculate the emf and, terminal p.d across the combination. [March 2014], 36. When two resistances are connected in series with a cell of emf 2V and negligible, internal resistance, a current of 2/5A flows in the circuit. When the resistances are, connected in parallel, the main current is 5/3A. Calculate the resistances. [March 2017], 37. A wire of length 2m, diameter 1mm and resistivity 1.963 × 10-8 Ω m is connected in, series with a battery of emf 3V and internal resistance 1Ω . Calculate the resistance of the, wire and the current in the circuit. [July 2016], 38. Two identical cells either in series or in parallel combination, gives the same current of, 0.5A through external resistance of 4 Ω . Find the emf and internal resistance of each cell., [June 2015]

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39. Two cells of emf 2V and 4V and internal resistance 1 Ω and 2 Ω respectively are, connected in parallel so as to send the current in the same direction through an external, resistance of 10 Ω . Find the potential difference across 10 Ω resistor. [March 2015], 40. The terminals of a cell of emf 1.5 V are connected to the ends of a 10 Ω coil. If the current, in the circuit is 140 mA, calculate the internal resistance of the cell., 41. Three resistors of resistance 12Ω, 8Ω and 4Ω are connected as shown in the, circuit diagram. Calculate the current in each branch of the circuit., , E=4V, r=2/3:, 42. In the given diagram, calculate the main current through the circuit and (ii)also current, through 9Ω resistor., 3V, , 0.24 , , 9, 6 , 3 , , 6 , 3, , , , 43. Three resistor 2Ω, 4Ω, 5Ω are connected in parallel. Calculate the total resistance of, combination. If combination is connected to a battery of emf 20V and negligible internal, resistance. Calculate current through each resistor and total current drawn from battery., 44. The number density of conduction electrons is 9.5x1028 m-3. Calculate the time taken by, an electron to drift from one end of the wire 4m long to the other end. The area of crosssection of the wire is 1.8x10-6 m2 and is carrying a current of 5 ampere., 45. Resistors of 2Ω and 4Ω are connected in parallel and a resistor of 1Ω is connected in, series with them. The combination is connected to a cell of emf 5V and internal, resistance of 1Ω. Calculate the current through the, 1Ω resistor., 46. In the given circuit, calculate the following:, (i), , effective resistance between A and B, (ii) current through the circuit, , and, , (iii) current through 3 resistor.

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47. Three resistors of 3 , 4  & 6  are connected in parallel. The combination is connected, to a cell of emf 2V and internal resistance, , 2,  . Calculate:, 3, , (i) effective resistance of the parallel combination, (iii) P. D. across the parallel combination, , (ii) current drawn from the cell, (iv) current through the 3, , resistance, 48. A uniform copper wire of length 2 m and cross-sectional area 5×10-7m2 carries a, current of 2 A. Assuming that there are 8×1028 free electrons per m3 of copper;, calculate the drift velocity of electrons. How long will an electron take to drift, from one end of the wire to the other?, 49. Two cells of emf 6V and 4V having internal resistance of 3Ω and 2 Ω respectively are, connected in parallel so as to send a current through an external resistance of 8 Ω in the, same direction. Find the current through the cells and the current through the external, resistance., 50. Two resistors of 8Ω and 12 Ω are connected in series across a battery of potential, difference 10 volt. Calculate the current in the circuit, when another unknown resistance, is connected in parallel with the two resistors across the same battery, the current in the, circuit changes to 2.5 A. Calculate the unknown resistance., 51. The four arms of a Wheat stone’s network ABCD have the following resistances. AB=2 Ω, , BC=4 Ω , CD=4 Ω and DA=8 Ω. A galvanometer of resistance 10 Ω is connected, between B and D. Find the current through the galvanometer, when the potential, difference between A and C is 5V., 52. A set of four cells, each of emf 2V and internal resistance 1.5Ω are connected across an, external load resistance of 10.5Ω with 2 rows, 2cells in each row. Calculate current in, each branch and potential difference across 10.5Ω resistor., 53. Calculate the temperature at which the resistance of a conductor becomes 15% more, than its resistance at 27C . The value of the temperature coefficient of resistance of the, conductor is 2.0 104 K ., 54. The magnetic fields at two points on the axis of a circular coil at a distance of 0.05m, and 0.2m from the centers are in the ratio 8:1. Find the radius of the coil., 55. A galvanometer of resistance 80Ω requires a current of 1mA for full scale, deflection. How to convert it into an voltmeter of range 0-10V and an ammeter of, range 0-5A., 56. A and B are two identical coils, of diameter 0.134m having 10 turns each. They are, placed concentrically with their planes at right angles to each other. A current of 1A, flows through each coil. Calculate the resultant magnetic field at their common, centre.

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57. A pure inductor of 25.0 mH is connected to a source of 220 V. Find the inductive, reactance and r.m.s current in the circuit if the frequency of the source is 50 Hz. [July, 2014], 58. An inductor and bulb are connected in series to an AC source of 220V, 50 Hz ac source., A current of 11A flows in the circuit and phase angle between voltage and current is π/4, radian. Calculate the impedance and inductance of the circuit. [July 2016], 59. A sinusoidal voltage of peak value 283 V and frequency 50 Hz is applied to a series LCR, circuit in which R = 3 Ω , L = 25.48 mH, and C = 796 μF. Find (a) the impendence of the, circuit; (b) the phase difference between the voltage across the source and the current (c), the power factor (d) Average power dissipated in the circuit. [March 2015], 60. A sinusoidal voltage of peak value 285 V is applied to a series LCR circuit in which R = 5, Ω , L = 28.5 mH, and C = 800 μF. Find (a) resonant frequency (b) Calculate the, impedance, current and power dissipated at resonance. [June 2017], 61. A resistor 100 Ω , a pure inductance coil of L = 0.5 H and capacitor are in series in a, circuit containing an ac of 200V, 50 Hz. In the circuit current is ahead of the voltage by, 30o. Find the value of the capacitance. [June 2015], 62. Obtain the resonant frequency of a series LCR circuit with L = 4.0 H, C = 27 μF and, R = 8.4 Ω .What is the Q-value of this circuit? Also find the band width. [March 2014,, March 2016], 63. A 20Ω resistor, 1.5 H inductor and 35µF capacitor are connected in series with a 220V; 50, Hz ac supply. Calculate the impendence of the circuit and also find the current through, the circuit.[june 2018], 64. A source of alternating emf of 220V, 50 Hz is connected in series with a resistance of, 200 Ω and inductance of 30μF. Does the current lead or lag the voltage and by what, angle? [March 2017], 65. A resistor, an inductor and a capacitor are connected in series with a 120V, 100Hz ac, source. Voltage leads the current by 35° in the circuit. If the resistance of the resistor is, 10W and the sum of inductive and capacitive reactance is 17 Ω, calculate the selfinductance of the inductor, 66. An inductance of 100 mH and a resistor of 50 Ω are connected in series to an ac source, of 230 V, 50 Hz, calculate the impedance, effective current and phase angle., 67. A series LCR circuit is connected to 220V AC source of variable frequency. The, inductance of the coil is 4H , capacitance of the capacitor is 4 F and resistance is 40 ., At resonance, calculate, , (a) the resonant frequency, , (b) current in the circuit (c) the, , inductive reactance., 68. In the given circuit, the potential difference across the, inductor L and resistor R are 200 V and 150 V respectively, and the r.m.s. value of current is 5 A. Calculate (i) the, impedance of the circuit and (ii) the phase angle between, the voltage and the current.

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69. A coil having inductance 0.2 H and resistance 10Ω is connected across 220V–50 Hz AC, source. Calculate (i) the current in the coil, (ii) the phase angle between the current and, supply voltage, (iii) power loss in the coil., 70. An inductor 200mH, capacitor 500μF, resistor 10 Ω are connected in series with a 100V, variable frequency ac source. Calculate (a) frequency at which power factor of the circuit, is unity. (b) Maximum current at that frequency. (c) Q-factor., 71. An ac source of 220V, 50Hz is connected in series with a series combination of capacitor, and a resistor of resistance 20Ω. Calculate The capacitance required to get a power factor, 0.5.The phase difference between the voltage and current, 72. A sinusoidal voltage of peak value 283V and frequency 50Hz is applied to a series, LCR circuit in which R=3Ω, L=25.38μH and C=796μF. Find, a. The impedance of the circuit, b. The phase difference between the voltage across the source and the current, c. Power dissipated in the circuit and (d) Power factor, 73. A series LCR circuit is connected to 220 V ac source of variable frequency. The, inductance of the coil is 5H, capacitance of the capacitor is 5 µF and resistance is 40 Ω. At, resonance calculate (a) Resonant frequency (b)Current in the circuit, (c) The inductive reactance., 74. A 80Ω resistor and 20µF capacitor are connected in series with an AC source of, 220 V-50Hz. Calculate potential difference across each of them., 75. A resistance of 600Ω, an inductor of 0.4H and a capacitor of 0.01µF are connected in, series to an AC source of variable frequency. Find the frequency of AC source for, which current in the circuit is maximum. Also calculate the bandwidth and quality, factor for the circuit., 76. A resistance of 50 Ω, an inductance of 10 mH and a capacitance 20µF are connected in, series to a 220V, 50 hz AC source. Calculate the current in the circuit and the power, factor., 77. An AC source of 220V, 50Hz is connected to a series combination of 20Ω resistor, 5μF, capacitor and 2mH inductor respectively. Calculate the (a) Inductive reactance and, capacitive reactance (b) Impedance (c) current (d) power factor., 78. A coil of inductance 0.5H and resistance 100Ω are connected to 200V 50Hz ac, supply. Find the maximum current in the coil. Also find the time lag between the, maximum voltage and the maximum current., 79. An inductor of unknown value, a capacitor of 100μF and a resistor of 10Ω are connected, series to 200V, 50Hz ac source. It is found that the power factor of the circuit is unity., Calculate the inductance of the inductor and maximum current in the circuit., 80. Two convex lenses of focal lengths 0.20 m and 0.30 m are kept in contact. Find the focal, length of the combination. Calculate powers of two lenses and combination. [March, 2014], 81. An equilateral prism produces a minimum deviation of 40o. What is the R.I of the, material of the prism? Calculate the angle of incidence. [July 2014], 82. The radii of curvature of two surfaces of a convex lens are 0.2m and 0.22m. Find the, focal length of the lens if refractive index of the material of lenses 1.5. Also find the, change in focal length, if it is immersed in water of refractive index 1.33. [june 2018]

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83. A converging lens of refractive index, , 3, and of focal length 15 cm in air, has the same, 2, , radii of curvature for both sides. If it is immersed in a water of refractive index, , 4, . Find, 3, , the focal length., 84. Two Plano- convex lenses are placed in contact such that their curved surfaces are facing, each other. The radius of curvature of the curved surfaces is 0.10cm and 0.15m, respectively. The space between them is filled with water of refractive index 1.33. If the, refractive index of glass is 1.5 find the focal length of the combination., 85. At what angle should a ray of light be incident on the face of a prism of refracting angle, 60o, so that it first suffers total internal reflection at other face? The refractive index of, the prism is 1.524., 86. A prism of angle 600 produces angle of minimum deviation of 400 . What is its R.I?, Calculate angle of incidence., 87. Light from a luminous point at the bottom of a glass slab of thickness 3cm strikes the, upper surface. The rays which are totally reflected at the top surface outline a circle of, radius 2.4 cm. Find RI of glass., 88. A ray of light is incident on one face of an equivalent prism of glass having refractive, index 1.55 at an angle of 40°; calculate the angle of deviation produced by the prism., 89.A convex lens of focal length 0.24 m and of refractive index 1.5 is completely immersed in, water of refractive index 1.33. Find the change in focal length of the lens., 90. Calculate the angle of minimum deviation produced by an equilateral prism of, refractive index 1.65., 91. A square of side 4.0cm is placed 20.0cm away from the concave mirror of radius of, curvature of 30cm. Calculate the area enclosed by the image of the square., 92. A compound microscope consists of an objective lens of focal length 2.0cm and an eyepiece of focal length 6.25cm separated by a distance of 15cm. How far from the objective, should an object be placed in order to obtain the final image at, (i) the least distance of distinct vision, (ii) at infinity?, 93. In young’s double slit experiment while using a source of wavelength 4500Å, the fringe, width obtained is 5mm. If the distance between the screen and plane of the slits is, reduced to half, what should be the wavelength of the light required to get fringes of, width 4mm? [July 2016], 94. In young’s double slit experiment while using a source of wavelength 6000Å, the fringe, width obtained is 6mm. If the distance between the screen and plane of the slits is, reduced to half, what should be the wavelength of the light required to get fringes of, width 4mm? [March 2017], 95. A beam of light consisting of two wavelengths 420 nm and 560 nm is used to obtain, interference fringes in Young’s double slit experiment. The distance between the slits is

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0.3 mm and the distance between the slits and the screen is 1.5 m. Compute the least, distance of the point from the central maximum, where the bright fringes due to both the, wavelengths coincide. [June 2015], 96. In Young’s double slit experiment, fringes of certain width are produced on the screen, kept at a certain distance from the slits. When the screen is moved away from the slits by, 0.1 m, fringe width increases by 60μm. The separation between the slits is 1 mm., Calculate wavelength of light used. [March 2016], 97. In Young’s double-slit experiment distance between the slits is 1 mm. The fringe width, is found to be 0.6 mm. When the screen is moved through a distance of 0.25 m the fringe, width becomes 0.75 mm. Find the wavelength of the light used. [March 2015], 98. In Young’s double slit experiment distance between the slits is 0.5 mm. When the screen, is kept at a distance of 100 cm from the slits the distance of 9th bright fringe from the, central fringe system is 8.835 mm. Find the wavelength of light used. [June 2017], 99. A beam of light consisting of two wavelengths 500 nm and 400 nm is used to obtain, interference fringes in Young's double slit experiment. The distance between the slits is, 0.3 mm and the distance between the slits and the screen is 1.5 m. Compute the least, distance of the point from the central maximum, where the bright fringes due to both the, wavelengths coincide., 100. In young’s double slit experiment, the distance between the slits is 1.2mm and the screen is, 0.75m from the slits. If the distance of the 5th fringe from the central fringe on the screen is, 1.8mm. Calculate the wavelength of light used. What will be the distance of the 5th dark, fringe from the centre of the screen?, 101. In Young’s double slit experiment the distance of the screen from the slits is 0.5m and the, distance between the slits is 1.5mm. If the distance of the fourth bright fringe from the center, of the screen is 0.8 mm. Calculate the wavelength of light used. What will be the distance of, the fifth dark fringe from the central point on the fringe?, 102. In a double slit experiment, the distance of the screen from the slits is 1 m and the distance, between the slits is 1mm. If the third dark fringe is formed at a distance 1.5 mm from the, central point on the screen, calculate the wavelength of light used., 103. In a Young’s double slit experiment light of wavelength 620nm is used to, Illuminate slits of width 0.3mm. A screen is placed at a distance of 0.9m., fringe width (b) distance between 5th and 9th bright fringe on screen., , Calculate, , 104. In Young’s double slit experiment the screen is at distance of 1.25m from the slit. When the, slits are illuminated by a light of wavelength 546nm, the width of 20 fringes is 8mm. Find the, separation between the slits. Find also the width of 20 fringes if yellow light of wavelength, 594nm is used., 105. In Young’s double -slit experiment the slit separation is 0.3mm and wavelength of light, used is 6500A0. A screen is placed 1m away from the slits. Calculate, (c) Distance of the 3rd bright fringe and, (d) Distance of the 2nd dark fringe from the central bright fringe., 106., In young’s interference experiment, two narrow parallel slits 0.2mm apart, are illuminated by a light of wavelength 600 nm to get interference fringe pattern

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on a screen 0.8 m away from the slits. Calculate the distance of (a) Third dark, fringe from the central fringe and (b) Second bright fringe from the central fringe., 107., The work function of caesium metal is 2.14 eV. When light of frequency 6 ×, 1014Hz is incident on the metal surface, photoemission of electrons occurs. What is the, (a) energy of the incident photons (b) maximum kinetic energy of the emitted electrons., (c) Stopping potential, and (d) maximum speed of the emitted photoelectrons? Given h =, 6.63 X 10-34 Js, e = 1.6 x 10-19 C, me = 9.1 × 10-31kg [July 2014], 108., , Light of wavelength 430 nm is incident on a) nickel surface of work function 5 eV, , and b) potassium surface of work function 2.3 eV. Find out from which metal electrons, area emitted. Also calculate the maximum velocity of electrons emitted from this metal., 109., , Ultraviolet light of wavelength 700 nm and 800nm are made to fall on, , hydrogen atoms in their ground state one after the other. Electrons with kinetic, energy 4.0 eV and 1.8 eV respectively are emitted. Calculate the value of Planck’s, constant., 110., , Find the maximum velocity of photoelectrons emitted by radiation of frequency, 3 1015 Hz from a photoelectric surface having a work function of 4.0 eV, , 111. Calculate the change in stopping potential for a photoelectron emitted from surface, if the wavelength of incident radiation reduced from 5900 A0 to 5000 A0., 112. Light of frequency 8×1015 Hz is incident on a substance of photo electric work, function 6.125 ev. Calculate the max velocity of the emitted photoelectrons., Given: the mass of the electron = 9.1×10-31 kg, Planck’s constant = 6.625×10-34 Js, 113. The threshold wavelength of metal is 2400 Å. Find the maximum kinetic energy of, photo electrons in eV, when light of wavelength 1500 Å is incident on its surface., 114. Calculate the shortest and longest wavelength of Ballmer series of hydrogen atom., Given R = 1.097 x 107 m-1. [March 2016], 115. The first member of the Balmer series of hydrogen atom has wavelength 6563Å., Calculate the wavelength and frequency of the second member of the same series., c = 3 × 108 ms-1. [March 2017], 116., The first member of the Balmer series of hydrogen atom has wavelength 6563A0., Calculate the wavelength and frequency of the second member of Paschen series., (Given: c = 3x108 ms-1)., 117., An electron transmission occurs from n=4 and n=1 energy level in hydrogen, atom. Find the wavelength of the emitted radiation if the energy of the electron in the, ground state is -13.6 eV. To which series does the spectral line belong?, 118., An electron transmission occurs from n=4 and n=2 energy level in hydrogen, atom. Find the wavelength of the emitted radiation if the energy of the electron in the, ground state is -13.6 eV. To which series does the spectral line belong?

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119., , Show that the total energy of an electron in the nth orbit of hydrogen atom is, , given by , , 13.6, eV . Hence calculate the energy needed to excite an electron from the 2 nd, n2, , orbit to the 4th orbit. If now the excited electron in the 4th orbit comes down the 2nd orbit,, what will be the wavelength of the emitted spectral line ? To which part of the, electromagnetic spectrum does this line belong ?, 120., Calculate the mass defect and specific binding energy of 7N14, given that the rest, mass of nitrogen nucleus is 14.00307 u, mP = 1.00783 u and mn = 1.00867 u. [March 2014], 121., Calculate binding energy and binding energy per nucleon of an oxygen nucleus, 16, 8O . Rest mass of oxygen nucleus is 15.995 u, mass of proton = 1.007825 u and mass of, neutron = 1.008665 u. [June 2017], 122., The activity of a radioactive substance is 4700 per minute. Five minutes later the, activity reduces to 2700 per minute. Find (a) decay constant (b) half-life of the, radioactive substance. [July 2016], 123., Determine the mass of Na22 which has an activity of 5 mCi. Half life of Na22 is 2.6, years. Avogadro number = 6.023 × 1023 [March 2015], 124., Calculate the half life and mean life of Radium 226 of activity 1Ci. Given mass of, Radium 226 is 1g. 226 g of radium consists of 6.023 × 1023 atoms. [June 2015], 125., The half life of a radioactive sample 3890 is 28 years. Calculate the rate of, disintegration of 15 mg of this isotope. Given Avogadro’s number = 6.023X1023., 126., The mass of lithium- 7 nucleus is 7.01022 u. Calculate the binding energy per, nucleon. Mass of proton = 1.00728 u and that of neutron = 1.00867 u., 127., Calculate the specific binding energies of 26Fe56 and 55Cs133. Given mass of 26Fe56, is 55.9349u and mass of 55Cs133 is 132.9049u. Mass of proton is 1.00728u and mass of, neutron is 1.00867u. State which of the nuclei is more stable., 128., Obtain the amount of 27Co60 necessary to provide a radioactive source of 8.0mCi, strength. The half life of of 27Co60 is 5.3 years., 129., , Calculate the half life and mean life of radium – 226 of activity 1 Ci; given the mass of, , radium – 226 is 1 gram and 266 gram of radium consists of 6.o23 x 1023 atoms., 130., , Calculate the energy released in Mev by 1g of U235 in the following fission, , reaction., 92U235 + 0n1 => 56Ba141 + 36Kr92 + 30n1, Given, mass of U235 = 235.04394 amu, mass of Kr92= 91.88544 amu, mass of Ba141= 140.91784 amu, mass of neutron = 1.00874 amu, 131., Calculate the energy released in Kilowatt hour when 0.2 kg of 92U235, undergoes fission completely. Assume that the average energy released per fission, of92U235nucleus is 200MeV.