Page 1 :
CHAPTER, , 20, , , , Electrons and Photons, , 1, The photoelectric threshold wavelength of, silver is 3250 x 107*° m. The velocity of the, electron ejected from a silver surface by, ultraviolet light of wavelength os, 2536 x 107° m is (Given, h = 4.14 10, eVs andc =3x 10° ms“') [NEET 2017], , (b) = 0.6x 10° ms, , (@) = 0.3x 10° ms, , fa) = 6 x 10° ms”, (c) = 61x 10° ms, 2. The de-Broglie wavelength of a neutron in, , thermal equilibrium with heavy water at a, temperature T (Kelvin) and mass m, is, , , , , , [NEET 2017], a )——, © Ime JamkT, gq () 27, ~ Samet <mkT, , 3. An electron of mass m and a photon have, same energy E.The ratio of de-Broglie, , wavelengths associated with them is, . INEET 2016], E\ i, ( a) (b) c(emeye, 1 1, 1(2m)\2z 1(E \2, (c) (<7 es, “(F) (rr, , (c being velocity of light), , 4. When a metallic surface is illuminated, with radiation of wavelength A, the, stopping potential is V. If the same surface, is illuminated with radiation of wavelength, , 2A, the stopping potential is : The, , threshold wavelength for the metallic, surface is INEET ~—, , 5, (a) 5A (o) a ’ ,, (c) 30 (d) 40,, 5. Electrons of mass m with de-Broglie, , wavelength A fall on the target in an Xray 5 i, tube. The cut-off wavelength (1.,) of the Ps), , , , , , emitted X-ray is INEET 2076; as?, 2menr? _ 2h, (a) Ao = A (0) A, a goat, att, amc?, (0) do = ~ (@) Ag =d , 6. Photons with energy 5 eV are incident ona, , cathode C in a photoelectric cell. The p=, maximum energy of emitted az, photoelectrons is 2 eV. When photons of ah, energy 6 eV are incident on C, no ,, , photoelectrons will reach the anode A, if At, , the stopping potential of A relative toCis ima, [NEET 2016) s3), (@) +3V Qo) +4V ()-1¥ @-3V yy, , 7. A radiation of energy ‘E’ falls normally on@ 2;, , perfectly reflecting surface. The 22g, , momentum transferred to the surface is i, , (c = velocity of light) [CBSE AIPMT 2015] wt, E, , 2E 2E E, & 2e 2E ace, @ oF OF a5, 8, A certain metallic surface is illuminated 1, with monochromatic light of wavelength \The stopping potential for photoelectric

Page 2 :
rons and Photons, ple, , for this light is 3V,. If the same, current is illuminated with light of, surlesngth 2A, the stopping potential is Vo., wav jreshold wavelength for this surface, ‘phe thres, , ectric effect is (CBSE AIPMT 2015), for photoel Oak © . =a ., aa © 4 6, , spich of the following figures represent, , W a ation of particle momentum and, , the yeociatedl de-Broglie wavelength?, , the as [CBSE AIPMT 2015], , Pp Pp, , @, >. >, , 4 photoelectric surface is illuminated, successively by monochromatic light of, , wavelength 2 and ry If the maximum, , kinetic energy of the emitted, photoelectrons in the second case is 3, times that in the first case, the work, function of the surface of the material is, , | IF Sail, , ide [CBSE AIPMT 2015], Tk (= Planck’s constant, c = speed of light), , he Ac 2he he, , ie oe oe, ay le, ae? OF OE OS, &, , . Light of wavelength 500 nm is incident on, 4 metal with work function 2.28 eV. The, de-Broglie wavelength of the emitted, electron is [CBSE AIPMT 2015], @)<2.8x 10" mm (b)< 2.8x 10-9 m, (22.8x 10-9 m (d)< 2.8x 10-2 m, , When the energy of the incident radiation, is increased by 20%, the kinetic energy of, photoelectrons emitted from a metal, surface increased from 0.5 eV to 0.8 eV., , * work function of the metal is, , =, , [CBSE AIPMT 2014], £065 ey (b) 1.0 eV, “13ey (d) 15eV, , 275, , 13. If the kinetic energy of the, , imes its, the Percentage cha, , wavelength of the, , Particle is, Previous value,, Nnge in the de-Broglie, particle is, , ICBSE AIPM 29, (c) 60 (d) 50 "a, , (a) 25 (b) 75, , 14, For Photoelectric emission from Certain, metal, the cut-off frequency is v, If, radiation of frequency 2 impinges on the, metal plate, the maximum possible, , velocity of the emitted electron wii be (m, , is the electron mass) (NEET 2013], hv hv 2h [hv, , a) /—— (b) JY (c) Jf =, , (a) Fe ©) m (2, , 15. The wavelength 1, of an electron and 4 pof, a photon of same energy E are related by, (NEET 2013], @) Ap = 0, , (DB) A, =A,, (ap « \he (a, <—, , Pe, , 16. Monochromatic radiation emitted when, electron state on hydrogen atom jumps, from first excited state to the ground state, irradiates a photosensitive material. The, stopping potential is measured to be 3.57 V., The threshold frequency of the material is, , [CBSE AIPMT 2012], (a) 4x 10'S Hz (0) 5x 10'S Hz, (c) 16 x 10'S Hz (d)2.5 x 10'S Hz, , 17. A 200 W sodium street lamp emits yellow, light of wavelength 0.6 um. Assuming it to, be 25% efficient in converting electrical, energy to light, the number of photons of, yellow light it emits per second is, , [CBSE AIPMT 2012], (a) 1.5 x 10” (b) 6x 10%, (c) 62 x 10? (d) 3x 10°, , 18. Light of two different frequencies whose, photons have energies 1 eV and 2.5 eV, respectively illuminate a metallic surface, whose work function is 0.5 eV, successively. Ratio of maximum speeds of, emitted electrons will be [CBSE AIPMT 2011], (a)1:2 (b) 1:1 (e) 1:5 (1:4

Page 3 :
276, , 19. Photoelectric emission occurs only when, the incident light has more than a certain, minimum (CBSE AIPMT 2011], , (a) wavelength (b) intensity, (c) frequency (d) power, , 20. In photoelectric emission process from a, metal of work function 1.8 eV, the kinetic, energy of most energetic electrons is 0.5, eV. The corresponding stopping potential, is [CBSE AIPMT 2011], , fa 13V (0) 05 V, (c)23V (@) 1.8V, , 21. A source S, is producing, 10'° photons/s of, wavelength 5000 A. Another source S, is, producing 102 x 10'* photons per second of, wavelength 5100 A. Then, (power of S,)/, (power of S,) is equal to [CBSE AIPMT 2010], , a) 1.00 (b) 1.02, c) 1.04 (d) 0.98, , 22. The number of photoelectrons emitted for, light of a frequency v (higher than the, threshold frequency vp) is proportional to, (a) v- [CBSE AIPMT 2009], (0) threshold frequency (Vp), , (c) intensity of light, (d) frequency of light (v), , 23. The figure shows a plot of photocurrent, versus anode potential for a photo sensitive, surface for three different radiations., Which one of the following is a correct, , statement ? [CBSE AIPMT 2009], Photo current, b., Oo a, , Retarding potential Anode potential, (a) Curves a and b represent incident radiations of, different frequencies and different intensities, (b) Curves a and b represent incident radiations of, same frequency but of different intensities, (c) Curves b and c represent incident radiations of, different frequencies and different intensities, (d) Curves b and c represent incident radiations of, same frequency having same intensity, , NEET Chapterwise Solutions - Pin, , a, 26. In the phenomenon of electric disct 30, ge, , 29. A 5 W source emits monochromatic ligh, , XN, , ' f, ochromatic light of w: pe), 24. ag produced by a helium sath . , i we, The power emitted is 9 mw mn Vadey fe 0, of photons arriving per second _ , 4, average at a target irradiated by this f ee, os 7 os (CBSE An bm! o, (ay9x 107 (b)3* 10" (6) 9x 1978 (a3 2m a, 25. A particle of mass 1 mg has the ” , ., wavelength as an electron move a%, wilocity of 3x 10° ms. The voloss’™®s ‘, article is (mass of electron rity of f Z, 0, , =9,.1x10 *' kg) [case Pn, , . Alper G, (a)2.7x 10°" ms" (0) 9x 10? mgs hg, Pini, (3x10 ms" (A) 2.7% 10 ng : o, , through gases at low pressure, the, , glow in the tube appears asa result of 6%, [CBSE, , (a) excitation of electrons in the tome MT, , (b) collision between the atoms of the gas 2 sci, , (c) collisions between the charged particies Jo, , emitted from the cathode and the atoms +. ;, , jas, @) Gilision between different electrons atte, atoms of the gas wy, 27. The work function of a surface of a ”, photosensitive material is 6.2 eV. The wavelength of the incident radiation for a, which the stopping potential is 5 V liesim ihe, the (CBSE AIPMT 2008} were, (a) ultraviolet region (b) visible region Socal, (c) infrared region (d) X-ray region } which, } wal, , 28. Monochromatic light of frequency, , 6.0x 10"* Hz is produced by a laser. Te, power emitted is 2 x 107° W. The pumbt = 24;, of photons emitted, on the average, bythe Rigg, , , , Leo,, source per second is [CBSE AIPMT20°, (a) 5x10 (0) Sx 10% ()5x10" Sx”, , a, , of wavelength 5000 A. When placed 05e, , away, it liberates photoelectrons, photosensitive metallic surface. Whe? be, source is moved to a distance of 10M,, number of photoelectrons liberate yt, reduced by a factor of [CBSE art, (a4 (b) 8 wre OF?

Page 4 :
d Photons, ns an, ct, ntum of a photon of energy, , g m/s, will be [CBSE AIPMT 2006], (d) 5x 107?, , ae BONN, , , Mev" Ki 10 *(c) 10, 033% 10°(b) 7 * >, , . charge tube ionisation of enclosed, , i” ed due to collisions between, , [CBSE AIPMT 2006], , ve ions and neutral atoms/molecules, , ve electrons and neutral atoms/ molecules, , s and neutral atoms/molecules, , gas atoms/molecules, , 4 — is produc, , posit!, (oF gal, , ') photon, id) neutral, ( tocell employs photoelectric effect to, A a [CBSE AIPMT 2006], col, , ) change in the frequency of light into a change, @ electric voltage a, , r) change in the intensity of illumination into a, , ° change in photoelectric current, , +) change in the intensity of illumination into a, * change in the work function of the photocathode, ig change in the frequency of light into a change, , in the electric current, , 4 photosensitive metallic surface has work, function, h Vo: If photons of energy 2 hvy, , fl] on this surface, the electrons come out, with a maximum velocity of 4x 10° m/s., When the photon energy is increased to, 5hv,, then maximum velocity of, photoelectrons will be | [CBSE AIPMT 2005], (@)2x 10° m/s (b) 2 x 10” m/s, , (8x 10° m/s (d) 8x 10° m/s, , The work functions for metals A, B and C, we respectively 1.92 eV, 2.0 eV and 5 eV., According to Einstein’s equation, the metals, which will emit photoelectrons for a, , radiation of wavelength 4100 A is/are, , [CBSE AIPMT 2005], (2) None of these (b) A only, , ()A and B only (d) All the three metals, , According to Einstein’s photoelectric, “uation, the graph between the kinetic, rgy of photoelectrons ejected and the, luency of incident radiation is, [CBSE AIPMT 2004], , (b), , =, Kinetic energy, Kinetic energy, , Frequency Frequency, , 277, , 124, , Frequency Frequency, 36. A photoelectric cell is illuminated point, a, source of light 1 m away. When tous is, shifted to 2 m, then [CBSE AIPMT 2003], , (a) each emitted electron carries halt the initial, energy, , (b) number of electrons emitted is a quarter of the, initial number, , (c) each emitted electron carries one quarter of, the initial energy, , (d) number of electrons emitted is half the initial, number, , 37. When ultraviolet rays are incident on, metal plate, the photoelectric effect does, not occur. It occurs by incidence of, , [CBSE AIPMT 2002], (a) infrared rays (b) X-rays, (c) radiowaves (d) light waves, , 38. Which of the following is not the property, of cathode rays? [CBSE AIPMT 2002], (a) It produces heating effect, (b) It does not deflect in electric field, , (c) Its casts shadow, (d) It produces fluorescence, , 39. The following particles are moving with the, same velocity, then maximum de-Broglie, , wavelength will be for [CBSE AIPMT 2002], (a) proton (b) a-particle, (c) neutron (d) B-particle, , 40. A light source is at a distance d from a, photoelectric cell, then the number of, photoelectrons emitted from the cell is n. If, the distance of light source and cell is, reduced to half, then the number of, photoelectrons emitted will become, , [CBSE AIPMT 2001], , a) ; (b)2n = ()4n_—, 41. The energy of a photon of light is 3 eV., , Then the wavelength of oo must 7, , (b) 412.50, , (a) 4125 nm, (d) 4nm, , (c) 41250 nm

Page 5 :
42. Einstein's work on photoelectric effect, gives support to [CBSE AIPMT 2000], (a) E=mce? (b) E=hv, (©) hv=1 mv? @e2 a, , 43. When intensity of incident light increases, , [CBSE AIPMT 1999], , (a) photocurrent increases, (0) photocurrent decreases, (c) kinetic energy of emitted photoelectrons, , increases, (d) kinetic energy of emitted photoelectrons, , decreases, 44, The photoelectric work function for a metal, surface is 4.125 eV. The cut-off wavelength, , for this surface is [CBSE AIPMT 1999], , (a) 4125A (6) 3000A (c)6000A (d) 2062.5A, , 45. In a photoemissive cell, with exciting, wavelength 2, the fastest electron has, speed v. If the exciting wavelength is, changed to 34/4, the speed of the fastest, emitted electron will be [CBSE AIPMT 1998], , (a) (2) : wv(4)”, aw, , V2 4 V2, (c) less than v (3) (d) greater than v (3), 46. Light of wavelength 5000 A falls on a, sensitive plate with photoelectric work, function of 1.9 eV. The kinetic energy of, the photoelectron emitted will be, [CBSE AIPMT 1998], (a)0.58eV (b)2.48eV (c) 1.24eV (d) 1.16 eV, , 47. The 21 cm radiowave emitted by hydrogen, in interstelar space is due to the interaction, called the hyperfine interaction in atomic, hydrogen. The energy of the emitted wave is, nearly [CBSE AIPMT 1998], , (a)10-7J (b) 1d (0) 7 x 10°F (d) 10-4, , 48. Which of the following is true ?, , ‘ [CBSE AIPMT 1997], (a) The stopping potential increases with, increasing intensity of incident light, (b) The photocurrent increases with increasing, intensity of light, (c) The current in photocell increases with, increasing frequency of light, (d) The photocurrent is proportional i, voltage led, , Y, , , , Photoelectric current will rise the, (6) when the energy of photons is 3.5 €¥., Photoelectric current will be maxi, , Chapterwise Solutions . |, NEET Phy ron, \ ge?, : Jectron of mass m and ch; ., , % eelerated from rest through a fee ig , Mor, difference of V volt in vacuum, Its lal ff h, speed will be {CBSE Aipy! @%,, , vy (c) [Zev ry fi, (8) om m |ev OG, i 2m, 0. The wavelength associated with an fe, , 3 accelerated through a potential diffe g Nie, 100 V, is of the order of [CBSE Ajpy, 8 air, (a) 100A (>) 100A (0) 105A ig, | i, , ) i, . If the threshold wavelength for a cor,: (rN, , 51 metal is 2000 A, then the work ianae @, the metal is [CBSE Alpyyr 4 p whé, (a) 6.2J (b)6.2eV (Cc) 6.2 MeV (gg, ‘ey (98, , 52. The nature of ions knocked out from hot a, surfaces is ICBSEAIPMT 145. | wav, (a) protons (b) electrons (c) neutrons (4) nuga, pho, , 53. Kinetic energy of an electron which ig wo!, accelerated in a potential difference of 1g), , Vis [CBSE AIPMT 10 | (2) 1, (a)1.6x10°7 J w16xir®y =|, ()1.6x107'J (d)1.6x 10 J @. An, 54. Gases begin to conduct electricity at low =, pressure, because [CBSE AIPMT 1954, sing, (a) at low pressures gases turn to plasma ele, (b) colliding electrons can acquire higher kinetic wil, energy due to increased mean free path fro, leading to ionisation of atoms :, (c) atoms break up into electrons and protons vel, (d) the electrons in atoms can move freely at ov cat, pressures @, 55. Doubly ionised helium atoms and ), hydrogen ions are accelerated from rest |{l. Th, through the same potential drop. Ther | ch, of the final velocities of the helium and |, hydrogen ion is [CBSE AIPMT 194 cu, 1 3, a> (b) 2 ©) s @2 b, 56. In photoelectric effect, the work functio®, ofa man is 3.5 eV. The emitted a ‘, can be stopped by applying a pote?, - 1.2 V. Then, [CBSE AIPMT am Xp, (2) the energy of the incident photons say dt, (b) the energy of the incident photons i> os, (C) if higher frequency photons be used: - ’