CBSE Class 12 Physics Dual Nature of Radiation Worksheet Set A

 

 

Question. The photoelectric work function for a metal surface is 4.125 eV. The cut-off wavelength for this surface is
(a) 4125 Å
(b) 3000 Å
(c) 6000 Å
(d) 2062 Å

Answer: B

Question. The energy of a photon of green light of wavelength 5000Å is
(a) 3.459 × 10^–19 joule
(b) 3.973 × 10^–19 joule
(c) 4.132 × 10^–19 joule
(d) 8453 × 10^–19 joule

Answer: B

Question. The photoelectric threshold of Tungsten is 2300Å. The energy of the electrons ejected from the surface by ultraviolet light of wavelength 1800Å is
(a) 0.15 eV
(b) 1.5 eV
(c) 15 eV
(d) 150 eV

Answer: A

Question. Which of the following when falls on a metal will emit photoelectrons ?
(a) UV radiations
(b) Infrared radiation
(c ) Radio waves
(d) Microwaves

Answer: A

Question. A light having wavelength 300 nm fall on a metal surface.
The work function of metal is 2.54 eV, what is stopping potential ?
(a) 2.3 V
(b) 2.59 V
(c) 1.59 V
(d) 1.29 V

Answer: C

Question. A and B are two metals with threshold frequencies 1.8 × 10¹⁴ Hz and 2.2 × 10¹⁴ Hz. Two identical photons of energy 0.825 eV each are incident on them. Then photoelectrons are emitted in (Take h = 6.6 × 10^–34 Js)
(a) B alone
(b) A alone
(c) neither A nor B
(d) both A and B.

Answer: B

Question. The photoelectric threshold wavelength of silver is 3250 × 10^–10m. The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength 2536 × 10^–10 m is (Given h = 4.14 × 10^–15 eVs and c = 3 × 10⁸ ms^–1) 
(a) ≈ 0.6 × 10⁶ ms^–1
(b) ≈ 61 × 10³ ms^–1
(c) ≈ 0.3 × 10⁶ ms^–1
(d) ≈ 6 × 10⁵ ms^–1

Answer: A,D

Question. An ionisation chamber, with parallel conducting plates as anode and cathodes has singly charged positive ions per cm³. The electrons are moving toward the anode with velocity 0.4 m/s. The current density from anode to cathode is X10⁴ m A/m². The velocity of positive ions moving towards cathode is
(a) 0.1 m/s
(b) 0.4 m/s
(c) zero
(d) 1.6 m/s

Answer: A

Question. The threshold frequency for photoelectric effect on sodium corresponds to a wavelength of 5000 Å. Its work function is
(a) 4 × 10^–19 J
(b) 1 J
(c) 2 × 10^–19 J
(d) 3 × 10^–19 J

Answer: A

Question. A particle is dropped from a height H. The de-Broglie wavelength of the particle as a function of height is proportional to
(a) H
(b) H^1/2
(c) H⁰
(d) H–^1/2

Answer: D

Question. Hard X-rays for the study of fractures in bones should have a minimum wavelength of 10^–11 m. The accelerating voltage for electrons in X-ray machine should be
(a) < 124 kV
(b) > 124 kV
(c) between 60 kV and 70 kV
(d) = 100 kV

Answer: A

Question. A parallel beam of light is incident normally on a plane surface absorbing 40% of the light and reflecting the rest. If the incident beam carries 60 watt of power, the force exerted by it on the surface is
(a) 3.2 × 10^–8 N
(b) 3.2 × 10^–7 N
(c) 5.12 × 10^–7 N
(d) 5.12 × 10^–8 N

Answer: B

Question. Radiations of two photon’s energy, twice and ten times the work function of metal are incident on the metal surface successsively. The ratio of maximum velocities of photoelectrons emitted in two cases is
(a) 1 : 2
(b) 1 : 3
(c) 1 : 4
(d) 1 : 1

Answer: B

Question. The momentum of a photon of wavelength λ is
(a) hλ
(b) h/λ
(c) λ/h
(d) h/cλ

Answer: B

Question. A photocell is illuminated by a small bright source placed 1 m away. When the same source of light is placed 2 m away, the number of electrons emitted by photocathode are reduced by a factor of
(a) 1/8
(b) 1/16
(c) 1/2
(d) 1/4

Answer: D

Question. The wavelength of K_α-line characteristic X-rays emitted by an element is 0.32 Å. The wavelength of K_β-line emitted by the same element will be
(a) 0.32 Å
(b) 0.39 Å
(c) 0.49 Å
(d) 0.27 Å

Answer: D

Question. Which metal will be suitable for a photoelectric cell using light of wavelength 4000Å. The work functions of sodium and copper are respectively 2.0 eV and 4.0 eV.
(a) Sodium
(b) Copper
(c) Both
(d) None of these

Answer: A

Question. Which one of the following graphs represents the variation of maximum kinetic energy (E_K) of the emitted electrons with frequency u in photoelectric effect correctly ? 

Answer: D

Question. The X-rays of wavelength 0.5 Å are scattered by a target.
What will be the energy of incident X-rays, if these are scattered at an angle of 72º ?
(a) 12.41 keV
(b) 6.2 keV
(c) 18.6 keV
(d) 24.82 keV

Answer: D

Question. In which of the following, emission of electrons does not take place?
(a) Thermionic emission
(b) X-rays emission
(c) Photoelectric emission
(d) Secondary emission

Answer: B

 

1 What is the stopping potential applied to a a photocell if the maximum kinetic energy of a photoelectron is 5eV ?

 

2 Work functions of two metals A and B are 4eV and 10 eV respectively . Which metal has the higher threshold wavelength ?

 

3 Two beams ,one of red light and the other of blue light , of same intrensity incident on a metallic surface to emit Photoelectrons. Which one of them emits electrons of greater kinetic energy?

 

4 How does the stopping potential of a Photo cell change ,when i) the intensity of the incident radiation is halved? Ii) frequency of incident radiation increases ?

 

5 If the potential difference used to accelerate electrons is tripled , by what factor the de Broglie wavelength of electron beam change?

 

6 An electron and proton have the same kinetic energy .Which one of them has the larger de Broglie wavelength.

 

7 An alpha particle and a proton are accelerated from rest by the same potential. Find the ratio of their de Broglie wavelengths.

 

8 Show graphically the variation of de Broglie wavelength λ of an electron with i)√V ii) V where V is the potential through which an electron is accelerated from rest.

 

9 Name the experiment which verified the wave nature of electrons. Which phenomenon was observed in this experiment using an electron beam?

 

10 Why Caesium oxide is coated on the cathode of Photo electric cell?

 

11 Why is the penetrating power of gamma rays more than that of beta and alpha radiations?

 

12 The figure shows plot of Kinetic energy of photoelectrons emitted with the frequency of incident radiation for two photosensitive materials A and B .

i) Which of them has more threshold wavelength ?

ii) Which of them has more work function?

iii) From which electrons will be emitted with more kinetic energy?

 

 

13 Two lines A and B in the plot given below show the variation of de Broglie wavelength λ versus √V, Where V is the accelerating potential difference, for two particles carrying the same charge. Which of the two represents a particle of small mass?

 

14 Are matter waves electromagnetic in nature ? What is the rest mass of a Photon?

 

15 What is the role of a moderator in a nuclear reactor? Explain its working .Mention the substance used as a moderator.

 

16 How do the neutron to Proton Ratio change during

i) β⁺ ii) β^- iii) α emission?

 

17 Name the particle which is emitted along with i) β^- particle ii) β⁺ particle . Why is it difficult to detect these particles ? 1(2006 S)

 

18 Define nuclear density and show that nuclear density does not depend on the mass and size of the nucleus.

 

19 Compare the nuclear radius ,volume ,and nuclear density of 4Be ⁸ and 13 Al²⁷ 

 

20 With a neat labeled diagram explain the experiment which verified the existence of Matter Waves. (2015)

 

21 Draw a graph between the potential energy of two nucleons as a function of separation between them mark the limit for attractive and repulsive forces. (2015)

 

22 Define K factor or Multiplication factor.