DUAL NATURE OF MATTER AND RADIATION
1. With what purpose was famous
Davisson-Gerber experiment with electrons performed?
2. How will the photoelectric current
change on decreasing the wavelength of incident radiation for a given
photosensitive material?
3. Name the experiment which establishes
the wave nature of a particle?
4. How does the ‘stopping
potential ‘in photoelectric emission depend upon
(i) the intensity of the incident
radiation
(ii)the frequency of the incident radiation?
(ii)the frequency of the incident radiation?
5. Show graphically how the stopping
potential for a given photosensitive surface varies with the frequency of the
incident radiation.
6. If the intensity of the incident
radiation on a photosensitive surface is doubled, how does the kinetic energy
of the emitted electrons get affected?
7. Define work function for a given
metallic surface?.Prove that the de-Broglie wavelength λ of electrons of energy E is given by, λ=h/√2mE
8. Two beams, one of red light and the
other of blue light, of the same intensity are incident on a metallic surface
to emit photoelectrons. Which one of the two beams emits elections of greater
kinetic energy?
9. A photon has velocity “c” and
frequency “v”. Write down the expression for its wavelength?.Establish Bohr’s
theory from de-Broglie’s hypothesis.
10. If the potential difference used to
accelerate electron is doubled, by what factor does the de-Broglie wavelength
of the electron beam change?
11. If the intensity of the incident
radiation in a photocell is increased, how does the stopping potential vary?
12. How does the maximum kinetic energy
of electrons emitted vary with the work function of the metal?
13. State two applications of photocell?.
X-ray rays of wavelength λ fall on a
photosensitive surface emitting electrons. Assuming that the work function of
the surface can be neglected, prove that the de-Broglie wavelength of electrons
emitted will be √(hλ/2mc).
14. On what factor does the energy
carried by a photon of light depend?.Prove that the product of the slope of ν-Vs
graph and electronic charge gives the value of Planck’s constant?
15. Why alkali metals are most suitable
for photoelectric emission?
16. A photon and an electron have the
same wavelength. Which particle is moving fasted?
17. What is the rest mass of a photon?.State
the properties of photons.
18. Are matter waves electromagnetic?
Write de-Broglie waves equation?
19. An electron and a proton are moving
in the same direction and possess same kinetic energy. Find the ratio of
de-Broglie wavelengths associated with these particles?
20. An election and a proton have the
same kinetic energy. Which of the two has a greater wavelength? Explain.
21. Define the term threshold frequency
and work function in relation to photoelectric effect?
22. Why is no electron emitted from a
plastic plate, when light incident on it?
23. Is there any difference between the
wave-length of the radiation and the de-Broglie wavelength of a photon of that
radiation?
24. Two metals X and Y when illuminated
with appropriate radiations emit photoelectrons. The work function of X is
higher than that of Y. Which metal will have higher value of threshold
frequency and why?
25. Green light ejects photoelectrons
from a given photosensitive surface whereas yellow light does not. What will
happen in case of violet and red light? Give reason for your answer?
26. What is meant by work function of a
metal? How does the value of work function influence the kinetic energy of
electrons liberated during photoelectric emission?
27. Define the terms ‘threshold
frequency’ and ‘stopping potential’ for photoelectric effect. Show graphically
how the stopping potential, for a given metal, varies with frequency of the
incident radiations. Mark threshold frequency on this graph?
28. Explain laws of photoelectric
emission on the basis of Einstein’s photoelectric equation?
29. An ᾳ-particle and a proton are accelerated though the same potential
difference. Calculate the radio of velocities acquired by the two particles?
30. Obtain the expression for the
maximum kinetic energy of the electrons emitted from a metal surface in terms
of the frequency of the incident radiation and the threshold frequency?
31. Draw a graph showing the variation
of stopping potential with frequency of incident radiations in relation to
photoelectric effect. Deduce an expression for the slope of this graph using
Einstein’s photoelectric equation?
32. Define the terms threshold frequency
and stopping potential in relation to the phenomenon of photoelectric effect.
How is the photoelectric current affected on increasing the (i) frequency (ii)
intensity of the incident radiations and why?
33. Sketch a graph between frequency of
incident radiations and stopping potential for a given photosensitive material.
What information can be obtained from the value of the intercept on the
potential axis?
34. Explain the laws of photoelectric
emission on the basis of Einstein’s photoelectric equation. Write one feature
of the photoelectric effect which cannot be explained on the basis of wave
theory of light.
35. Mention the significance of
Davisson-Germer experiment. An ᾳ-particle and a proton are
accelerated from rest through the same potential difference V. Find the ratio
of de-Broglie wavelength associated with them.
36. Red light, however bright it is, cannot
produce the emission of electrons from a clean zinc surface. But even weak
ultraviolet radiation can do so. Why?
-AJAY KUMAR SHARMA
