Untitled Document

Question Bank No: 1

1. Which of the following statements are correct
(i)electron was discovered by Nillikan
(ii)The mass of each positive ion is nearly equal to the mass of the gas atom
(iii)Cathode rays are slow moving electrons
(iv)electron is a fundamental particle

a)		(i) and (iv)
b)		(i) and (iii)
c)		(i), (ii) and (iii)
d)		(ii), (iii) and (iv)

2. The slope of frequency of incident light and stopping potential for a given surface will be

a)		h
b)		h/e
c)		eh
d)		e

3. The threshold wave length is 2000 $A^{0}$ .The work function is

a)		6.25eV
b)		6.2 eV
c)		6.2 MeV
d)		6.2 KeV

4. The uncertainity in the position of proton is 6 $\times 10^{- 8} m$ then the minimum uncertainity in its speed will be

a)		1 cm/s
b)		1m/s
c)		1mm/s
d)		100mm/s

5. The threshold frequency for photo electric effect on sodium corresponds to a wave length of 5000 $A^{0} .$ Its work function is

a)		4 $\times 10^{- 19} J$
b)		1J
c)		2 $\times 10^{- 19} J$
d)		3 $\times 10^{- 19} J$

6. The maximum K.E of photo electrons emitted from a surface when the photons of energy 5.6eV falls on it, is 4eV, the stopping potential in volts is

a)		1.6V
b)		3.2V
c)		4V
d)		9.6V

7. Ultra violet radiations of 6.2eV falls on an aluminium surface (work function 4.2 eV) Thus K.E in joule of the fastest electron emitted is approximately

a)		3.2 $\times 10^{- 21}$
b)		3.2 $\times 10^{- 19}$
c)		3.2 $\times 10^{- 17}$
d)		3.2 $\times 10^{- 15}$

8. A radio transmitter operates at a frequency 1000 KHZ and a power of 66KW. Find the number of photons emitted per second

a)		$10^{27}$
b)		$10^{28}$
c)		$10^{29}$
d)		$10^{30}$

9. Plank's constant has the dimension of

a)		energy
b)		mass
c)		frequency
d)		angular momentom

10. An electron with rest mass $m_{0}$ moves with a speed of 0.8C. Its mass when it moves with this speed is

a)		$m_{0}$
b)		$m_{0} / 6$
c)		5 $m_{0} / 3$
d)		3 $m_{0} / 5$

11. Resistance of discharge tube is

a)		ohmic
b)		non-ohmic
c)		zero
d)		none of these

12. If frequency of the waves emitted from a ratio stations is 6 Mega Hertz. Then wavelength of waves will be

a)		24 m
b)		12 m
c)		6 m
d)		50 m

13. Wavelength associated with an electron of energy 100 eV is

a)		0.12 $\overset{\circ}{A}$
b)		12.0 $\overset{\circ}{A}$
c)		1.2 $\overset{\circ}{A}$
d)		6.3 $\overset{\circ}{A}$

14. A beam of $α$ particles passes undeflected through crosses electric and magnetic fields with F = 6.6 $\times 10^{6}$ N $C^{- 1}$ and B= 1.2 T. Then speed of $α$ -particles in m/s will be

a)		1.1 $\times 10^{6}$
b)		5.5 $\times 10^{6}$
c)		7.8 $\times 10^{6}$
d)		1.8 $\times 10^{6}$

15. The work required to move an electron between the plates whose potential difference is 3 million volts is

a)		5.6 $\times 10^{6}$ J
b)		4.8 J
c)		4.8 $\times 10^{- 19}$ J
d)		4.8 $\times 10^{- 13}$ J

16. If threshold wave length of a material is 350nm, then which one of the following sources will show photoemission ?

a)		A 200 W fluorescent bulb
b)		A 200 W infrared bulb
c)		A ruby laser source of 0.5 W
d)		An ultraviolet lamp of 0.5 W

17. A ratio transmitter operates at a frequency of 880 kHz and a power of 10 kW. The number of photos emitted per second is

a)		1.71 $\times 10^{31}$
b)		1327 $\times 10^{34}$
c)		13.27 $\times 10^{24}$
d)		13.27 $\times 10^{44}$

18. Kinetic energy of a particle becomes 4 times, then how many times will its de-Broglie wavelength become

a)		1/4
b)		1/2
c)		2
d)		4

19. The momentum of a particle of mass m and charge q is equal to that of a photon of wavelength $λ$ . Then the speed of the particle is given by

a)		$\frac{mh}{λ}$
b)		$\frac{h}{m λ}$
c)		$\frac{h λ}{qm}$
d)		qh $λ$

20. Three particles having charges in the ratio of 1:2:3 produce the same point on the photographic film in the thomson experiment. Their masses are in the ratio of

a)		1:2:3
b)		2:3:1
c)		3:2:1
d)		1:3:2

21. A particle of mass M initially at rest decays into two particles of masses $m_{1}$ and $m_{2}$ having some velocities. The ratio of the de broglie wavelength of the particles is

a)		$\frac{m_{2}}{m_{1}}$
b)		$\frac{m_{1}}{m_{2}}$
c)		1 : 1
d)		$\sqrt{\frac{m_{2}}{m_{1}}}$

22. The maximum kinetic energy of photo electrons emitted from a surface when photons of energy 6 eV fall on it is 4 eV. The stopping potential is

a)		2 V
b)		4 V
c)		6 V
d)		10 V

23. UV-radiation of 7.2 eV is incident on a photosensitive surface. If the work function of the surface is 5.4 eV, then the maximum velocity of the emitted photoelectrons is nearly

a)		2 $\times 10^{6} m / \sec$
b)		10 $\times 10^{5} m / \sec$
c)		4 $\times 10^{6} m / \sec$
d)		8 $\times 10^{5} m / \sec$

24. The stopping potential as a function of frequency of incident radiation is plotted for two different photoelectric surfaces A and B as shown in figure. electronandprotons-q5 The graphs shows that the work function of A is

a)		same as that of B
b)		smaller than that of B
c)		greater than that of B
d)		no comparison can be done from given graphs

25. The specific charge of an electron is

a)		1.6 $\times 10^{- 19}$ coulomb
b)		5.7 $\times 10^{- 12}$ kg / C
c)		1.76 $\times 10^{11}$ C/ kg
d)		9.1 $\times 10^{- 31}$ kg

26. In a discharge tube at 0.02mm there is a formation of

a)		CDS
b)		FDS
c)		both space
d)		none of these

27. If the energy of a photon of wavelength of 6,000 A is 3.32 $\times 10^{- 19}$ J, the photon energy for a wavelength of 4,000A will be

a)		4.98 $\times 10^{- 19}$ J
b)		4.44 $\times 10^{- 19}$ J
c)		2.22 $\times 10^{- 19}$ J
d)		1.11 $\times 10^{- 19}$ J

28. X-ray tubes operates at 10KV. The ratio of x-ray wavelength to that of de-broglie wavelength is

a)		4.7
b)		6.87
c)		10.062
d)		8.34

29. If $n_{r}$ and $n_{b}$ are the numbers of photons emitted by a red bulb and blue blub respectively of equal power in a given time. Then

a)		$n_{r} = n_{b}$
b)		$n_{r} > n_{b}$
c)		$n_{r} < n_{b}$
d)		information is insufficient

30. The threshold wavelength for photoelectric emission from a material is 5200 A. Photo electrons will be emitted when this material is illuminated with monochromatic radiations from a

a)		50 Watt ultraviolet lamp
b)		1 Watt ultraviolet lamp
c)		50 Watt infrared lamp
d)		1 Watt infrared lamp

31. Doubly ionized helium atoms and hydrogen ions are accelerated from rest through the same potential drop. The ration of the final velocities of the helium and the hydrogen ions is

a)		1/2
b)		2
c)		1/ $\sqrt{2}$
d)		$\sqrt{2}$

32. When the energy of the incident radiation is increased by 20% then K.E of the photoelectrons emitted from a metal increases from 0.5 eV to 0.8 eV. The work function of the metal is

a)		1.0 eV
b)		1.3 eV
c)		0.65 eV
d)		1.5 eV

33. In an oscilloscope the focusing of beam on the screen is achieved by

a)		convex lenses
b)		magnetic field
c)		electric potential
d)		all of the above

34. When the light of wavelength 2537 $\overset{\circ}{A}$ is incident over the photosensitive surface, the stopping voltage 0.24 volt is required to stop the fastest photoelectron. The threshold frequency for the surface is

a)		2.248 $\times 10^{15} Hz$
b)		1.414 $\times 10^{14} Hz$
c)		1.124 $\times 10^{15} Hz$
d)		none of these

35. The number of electrons ejected depends on

a)		the frequency
b)		the intensity
c)		both on intensity and frequency
d)		neither intensity nor frequency of the radiations

36. If the momentum of a particle is doubled, then wavelength associated with the particle will

a)		remain unchanged
b)		become half
c)		become double
d)		none of these

37. If the K.E of the most energetic photoelectrons emitted from a photosensitive surface is doubled when the wavelength of the incident radiation is reduced from $λ_{1}$ to $λ_{2}$ . Then work function of the metal is

a)		$\frac{hc}{λ_{1} λ_{2}} (λ_{1} - λ_{2})$
b)		$\frac{hc}{λ_{1} λ_{2}} (λ_{1} + λ_{2})$
c)		$\frac{hc}{λ_{1} λ_{2}} ({2 λ}_{1} - λ_{2})$
d)		$\frac{hc}{λ_{1} λ_{2}} ({2 λ}_{2} - λ_{1})$

38. A cathode emits 1.8 $\times 10^{17}$ electrons per second when heated. When 400 volts is applied to the anode all the electrons emitted each the anode. The maximum anode current is

a)		$10^{- 11} A$
b)		29 mA
c)		$10^{11} A$
d)		11.6 A

39. The quantization of charge is proved by the experiment of

a)		Millikan's oil drop method
b)		Compton scattering
c)		Raman's scattering
d)		Davisson Germer

40. If $λ$ is de-Broglie wavelength for a photon accelerated through a potential difference of 100 V, the de-Broglie wavelength for an $α$ - particle accelerated through the same potential difference will be

a)		$λ / 2$
b)		$λ / \sqrt{2}$
c)		2 $\sqrt{2} λ$
d)		$λ / 2 \sqrt{2}$

41. In a mass spectograph, an ion X of mass number 24 and charge +e and another ion Y of mass number 22 and charge +2e, enter in a perpendicular magnetic field with the same velocity. The ration of the radii of their circular paths in the field will be

a)		11/22
b)		24/11
c)		22/11
d)		11/2

42. The cathode rays travel with the speed

a)		equal to 3 $\times 10^{8} m / s$
b)		less than 3 $\times 10^{8} m / s$
c)		greater than 3 $\times 10^{8} m / s$
d)		may be less than, greater than or equla to 3 $\times 10^{8} m / s$

43. The work function og a photosensitive surface is 5.18 eV. The photoelectrons are emitted when light of wavelength 2,000 $\overset{\circ}{A}$ falls on it. The potential difference applied to stop the fastest photoelectrons is

a)		1.0 V
b)		2.24 V
c)		2.4 V
d)		4.8 V

44. An electric field of intensity 6 $\times 10^{4}$ volts / m is applied perpendicular to the direction of motion of the electron. A magnetic field of intensity 8 $\times 10^{- 2}$ T is applied perpendicular to both the electric field and direction of motion of the electron. What is the velocity of the electron if it passes undeflected?

a)		7.5 $\times 10^{5} m / s$
b)		7.5 $\times {- 10}^{5} m / s$
c)		6 $\times 10^{4} m / s$
d)		8 $\times 10^{- 2} m / s$

45. Which of the following statement is correct?

a)		Photo-current increases with increase in applied voltage
b)		Photo-current increases with increase in frequency of light
c)		Photo-current increases with increase in intensity of light
d)		None of these

46. Two photons of energies twice and thrice the work function of a metal are incident on the metal surface. Then the ratio of maximum velocities of the photoelectrons emitted in the two cases respectively, is

a)		$\sqrt{2}$ : 1
b)		1 : $\sqrt{2}$
c)		$\sqrt{3}$ : 3
d)		$\sqrt{3}$ : $\sqrt{2}$

47. Photoelectrons are emitted from a metal surface only when

a)		metal is initially charges
b)		wavelength of incident light is less than some maximum limit
c)		frequency of incident light is less than some minimum value
d)		incident angle should be greater than the critical angle

48. In Millikans oil drop experiment, a drop of radius r, carrying a charge q is in equilibrium between the plates at a potential difference V. Then, another drop of radius 2r will be stationary at a potential difference 4 V if it carries a charge

a)		q/2
b)		2q
c)		4q
d)		q/4