Physics: Dual nature of radiation and Matter Test

 

Physics Test (50 Marks)

Chapter: Dual Nature of Radiation and Matter
Time: 2 Hour

Section A:

 Q.1) Multiple Choice Questions (10 marks)

1. A photocell used in street lights works with:
   a) Infrared    b) Visible    c) UV    d) X-rays
2. Cathode material suitable for photoelectric effect:
   a) Zinc    b) Aluminium    c) Nickel    d) Potassium
3. Stopping potential depends on:
   a) Average wavelength
   b) Longest wavelength
   c) Shortest wavelength
   d) Intensity
4. Longest de Broglie wavelength (same KE):
   a) Electron    b) Proton    c) Alpha    d) Hydrogen atom
5. For equal power sources:
   a) Red < Blue photons
   b) Red = Blue
   c) Red > Blue
   d) None
6. Equation E = pc is valid for:
   a) Electron    b) Photon    c) Both    d) None
7. Increasing intensity increases:
   a) KE
   b) Stopping potential
   c) Number of electrons
   d) Work function
8. Threshold frequency depends on:
   a) Intensity    b) Material    c) Distance    d) Voltage
9. de Broglie wavelength is inversely proportional to:
   a) Velocity    b) Momentum    c) Charge    d) Time
10. Photoelectric effect proves:
    a) Wave nature
    b) Particle nature
    c) Both
    d) None

Section B: 

Q.2) Answer in One Sentence (Attempt any 10 out of 12) 

(10 marks)

11. Define photoelectric effect.
12. What is work function?
13. Define stopping potential.
14. What is threshold frequency?
15. Define photon.
16. What is de Broglie wavelength?
17. Can a stationary electron have wavelength?
18. What is wave-particle duality?
19. What happens when frequency is below threshold?
20. State one use of photocell.
21. What is photocurrent?
22. State one property of photons.

Section C: 

Q.3) Answer in Short (Attempt any 8 out of 10)(16 marks)

23. Why does red light not produce photoelectric effect in some cases?
24. Can microwaves be used for photoelectric effect? Explain.
25. Explain why kinetic energy does not depend on intensity.
26. Explain inverse relation between stopping potential and wavelength.
27. What happens to extra energy of incident radiation?
28. Explain de Broglie hypothesis.
29. State importance of Davisson–Germer experiment.
30. Compare photon and electron.
31. What is threshold wavelength?
32. Why does photocurrent increase with intensity?

Section D

Q.4) Solve the Following Numericals (Attempt any 7 out of 9) (14 marks)

1. Monochromatic light of frequency 6 × 10¹⁴ Hz is incident on a metal surface having work function 2.0 eV.
Calculate:
(i) Maximum kinetic energy of emitted electrons
(ii) Stopping potential

2. The threshold wavelength of a metal is 5000 Å. Light of wavelength 3000 Å is incident on it.
Calculate the maximum kinetic energy of emitted electrons.

3. In a photoelectric experiment, stopping potential is found to be 1.5 V when light of frequency 7 × 10¹⁴ Hz is used.
Calculate the work function of the metal.

4. An electron is accelerated through a potential difference of 100 V.
Calculate:
(i) Its velocity
(ii) Its de Broglie wavelength

5. Light of wavelength 4000 Å falls on a metal and the stopping potential is 1.2 V.

Calculate:(i) Work function of the metal (ii) Threshold wavelength

6.An electron and a proton have the same de Broglie wavelength.
Find the ratio of:
(i) Their momenta
(ii) Their kinetic energies

7. The slope of the graph between stopping potential and frequency is 4.1 × 10^-15 V·s.
Calculate Planck’s constant.
(Given: charge of electron = 1.6 × 10^-19 C)

8. An electron has kinetic energy of 200 eV.
Calculate:
(i) Its momentum
(ii) Its de Broglie wavelength

9. Radiation of frequency 8 × 10¹⁴ Hz ejects electrons with maximum kinetic energy 1.5 eV.
Calculate:
(i) Work function of the metal
(ii) Threshold frequency