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Question Bank No: 1

1. If $Δ x$ and $Δ p$ are the uncertainities in the measurement of position and momentum of the particle, then according to Heisenberg principle

a)		$Δ x \times Δ p$ $\geq h$
b)		$Δ x \times Δ p < h$
c)		$Δ x \times Δ p$ $> h^{2}$
d)		$Δ x \times Δ p$ $< h^{2}$

2. Solar cell is a

a)		photo volatic cell
b)		photo conductive cell
c)		photo emission cell
d)		button cell

3. What advantage might an elctron microscope have over an optical microscope

a)		electrons are more powerful
b)		greater resolution
c)		longer wavelengths are possible
d)		electrons can be focussed easily

4. Which of the following graphs represents the variation of momentum of a particle and associated de Broglie wave length

a)
b)
c)
d)

5. Neglecting relativistic change of mass, the wavelength associated with an electron of kinetic energy E is proporational to

a)		$E^{1 / 2}$
b)		$E^{- 1 / 2}$
c)		E
d)		$E^{- 1}$

6. Matter waves are

a)		e. m waves
b)		transverse waves
c)		longitudinal waves
d)		waves which exhibit diffraction

7. The photoelectric effect the slop of the graph, stopping potential $V_{0}$ against frequency $f$ gives

a)		ratio of planck's constant to charge of election
b)		charge of electron
c)		work function of the emitter
d)		plank's constant

8. The idea of quantum nature of radiation has first emerged in an attempt to explain

a)		thermionic emission
b)		radio activity
c)		black body radiation
d)		atom model

9. Light of frequency 1.5 times threshold frequency is incident on a photosensitive surface. The frequency halved and intensity doubled, the photo electric current becomes

a)		halved
b)		doubled
c)		quadrapled
d)		zero

10. The momentum of a photon is P. The corresponding wave length is

a)		$\frac{h}{P}$
b)		$h P$
c)		$P / h$
d)		$h \sqrt{P}$

11. If the energy of a photon corresponding to wavelength 600nm is ${3.32 \times 10}^{- 19} J$ , the photon energy for wave length 400nm is

a)		${1.11 \times 10}^{- 19} J$
b)		${2.22 \times 10}^{- 19} J$
c)		${3.32 \times 10}^{- 19} J$
d)		${4.98 \times 10}^{- 19} J$

12. Light of two different frequencies whose photons have energies 1eV and 2.5eV successively illuminate a metal surface of work function 0.5eV. The ratio of the maximum speeds of the emitted electron will be

a)		1 : 5
b)		5 : 1
c)		1 : 2
d)		1 : 1

13. Imagine that you are sitting in a room with your back to one wall. A beam of cathode rays travelling horizontally from the back wall towards the front wall is deflected to the right by a magnetic field. The direction of the field that exist in the room is

a)		vertically upwards
b)		vertically downwards
c)		horizontally from left to right
d)		none of the above

14. An electron is accelerated through a potential difference of 10kv. Its velocity is nearly $[e / m = {1.8 \times 10}^{11} c / kg]$

a)		${6 \times 10}^{7} m / s$
b)		${1 \times 9}^{7} m / s$
c)		${5 \times 10}^{7} m / s$
d)		${3.3 \times 10}^{6} m / s$

15. A proton, duetron and an alpha particle are accelerated from rest to same accelerating potential. The velocity acquired by them will be in the ratio

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

16. Free electrons are held inside the metal by attactive forces at the surface and the minimum amount of energy required for their escape from the metal is called

a)		thermal energy
b)		photon energy
c)		work function
d)		kinetic energy

17. The momentum of a photon of energy $h f$ is

a)		$h f$
b)		$h f c$
c)		$\frac{h f}{c}$
d)		has no momentum

18. A surface ejects electrons when hit by green light and not ejected by yellow light. Will electron be ejected if hit by red light?

a)		yes
b)		no
c)		yes if the beam is intense
d)		none of the above

19. Cathode rays are

a)		fast moving protons
b)		fast moving electrons
c)		fast moving neutrons
d)		e. m waves

20. The stopping voltage in photoelectric effect depends on

a)		the frequency of the incident photons only
b)		nature of the metal surface only
c)		intensity of the incident light
d)		frequency of the incident light as well as nature of the metal

21. The number of photoelectrons emitted from a given emitter depends upon

a)		intensity of incident light
b)		frequency of the incident light
c)		wave length of the incident light
d)		the color of the light

22. The work function of aluminium surface is 4.2 cv. The cut off wave length for photoelectric effect for the surface is about

a)		${2500 A}^{\circ}$
b)		${3000 A}^{\circ}$
c)		${4200 A}^{\circ}$
d)		${1478 A}^{\circ}$

23. The threshold wave length of a metallic surface is $λ_{0}$ the photoelectric work function is

a)		$\frac{hc}{λ_{0}}$
b)		$\frac{h λ_{0}}{c}$
c)		${hc λ}_{0}$
d)		${h λ}_{0}$

24. The photoelectric phenomenon was first explained by

a)		Bohr
b)		Planck
c)		Millikan
d)		Einstein

25. The specific charge of cathode rays

a)		depends on the nature of the gas in the tube
b)		is a constant
c)		depends on the metal used for cathode
d)		depends on the applied voltage and prenuxl