Dual Nature of Matter and Radiation MCQs
1. Light of frequency 1.9 times the threshold frequency is incident on a photosensitive material. If the frequency is halved and intensity is doubled, the photocurrent becomes
a) doubled
b) quadrupled
c) halved
d) zero
Answer: (d) zero
2. For a metal having a work function W0, the threshold wavelength is λ. What is the threshold wavelength for the metal having work function 2W0?
a) λ/4
b) λ/2
c) 2λ
d) 4λ
Answer: (b) λ/2
3. Radiation of frequency ν is incident on a photosensitive metal. When the frequency of the incident radiation is doubled, what is the maximum kinetic energy of the photoelectrons?
a) 4E
b) 2E
c) E + hν
d) E – hν
Answer: (c) E + hν
4. Calculate the de Broglie wavelength associated with the electron which has a kinetic energy of 5 eV.
a) 5.47 Å
b) 2.7 Å
c) 5.9 Å
d) None of the above
Answer: (a) 5.47 Å
5. What is the ratio of the de Broglie wavelengths proton and an α particle if they are accelerated by the same potential difference?
a) 2√2: 1
b) 3:2
c) 3√2: 1
d) 2: 1
Answer: (a) 2√2: 1
6. In photoelectric effect what determines the maximum velocity of the electron reacting with the collector?
a) Frequency of incident radiation alone
b) The potential difference between the emitter and the collector
c) The work function of metal
d) All of these
Answer: (d) All of these
7. Who among the following established that electric charge is quantised?
a) R.A. Millikan
b) Wilhelm Rontgen
c) William Crookes
d) J.J. Thomson
Answer: (a) R.A. Millikan
8. By which of the following physical processes can minimum energy required for the electron emission from the metal surface be supplied to the free electrons?
a) Field emission
b) Thermionic emission
c) Photoelectric emission
d) All of these
Answer: (d) All of these
9. Which of the following statements is true regarding the photoelectric experiment?
a) The stopping potential increases with the increase in the intensity of incident light.
b) The photocurrent increases with the intensity of light.
c) The photocurrent increases with the increase in frequency
d) All of the above
Answer: (b) The photocurrent increases with the intensity of light.
