# Physics class 12 chapter 11 Objective Questions

## Dual Nature of Radiation and Matter Objective

1. Who established that electric charge is quantised?

(a) J.J. Thomson

(b) William Crookes

(c) R.A. Millikan

(d) Wilhelm Rontgen

Answer: (c) R.A. Millikan

1. Cathode rays were discovered by

(a) Maxwell Clerk James

(b) Heinrich Hertz

(c) William Crookes

(d) J.J. Thomson

Answer: (c) William Crookes

1. The minimum energy required for the electron emission from the metal surface can be supplied to the free electrons by which of the following physical processes?

(a) Thermionic emission

(b) Field emission

(c) Photoelectric emission

(d) All of these

Answer: (d) All of these

1. The phenomenon of photoelectric emission was discovered in 1887 by

(a) Albert Einstein

(b) Heinrich Hertz

(c) Wilhelm Hallwachs

(d) Philipp Lenard

Answer: (b) Heinrich Hertz

1. A metal surface ejects electrons when hit by green light but nothing when hit by yellow light. The electrons will be ejected when the surface is hit by

(a) blue light

(b) heat rays

(c) infrared light

(d) red light

Answer: (a) blue light

1. Which of the following statements is correct regarding the photoelectric experiment?

(a) The photocurrent increases with intensity of light.

(b) Stopping potential increases with increase in intensity of incident light.

(c) The photocurrent increases with increase in frequency.

(d) All of these

Answer: (a) The photocurrent increases with intensity of light.

1. In photoelectric effect, the photocurrent

(a) depends both on intensity and frequency of the incident light.

(b) does not depend on the frequency of incident light but depends on the intensity of the inci-dent light.

(c) decreases with increase in frequency of inci-dent light.

(d) increases with increase in frequency of inci-dent light.

Answer: (b) does not depend on the frequency of incident light but depends on the intensity of the inci-dent light.

1. The maximum value of photoelectric current is called

(a) base current

(b) saturation current

(c) collector current

(d) emitter current

Answer: (b) saturation current

1. In photoelectric effect, the photoelectric current is independent of

(a) intensity of incident light

(b) potential difference applied between the two electrodes

(c) the nature of emitter material

(d) frequency of incident light

Answer: (d) frequency of incident light

1. In photoelectric effect, stopping potential depends on

(a) frequency of incident light

(b) nature of the emitter material

(c) intensity of incident light

(d) both (a) and (b)

Answer: (d) both (a) and (b)

1. According to Einstein’s photoelectric equation, the graph of kinetic energy of the photoelectron emitted from the metal versus the frequency of the incident radiation gives a straight line graph, whose slope

(a) depends on the intensity of the incident radi-ation.

(b) depends on the nature of the metal and also on the intensity of incident radiation.

(c) is same for all metals and independent of the intensity of the incident radiation.

(d) depends on the nature of the metal.

Answer: (c) is same for all metals and independent of the intensity of the incident radiation.

1. Which phenomenon best supports the theory that matter has a wave nature?

(a) Electron momentum

(b) Electron diffraction

(c) Photon momentum

(d) Photon diffraction

Answer: (b) Electron diffraction

1. Which of the following radiations cannot eject photo electrons ?

(A) ultraviolet

(B) infrared

(C) visible

(D) X-rays

1. Evidence of the wave nature of light cannot be obtained from:

(A) diffraction

(B) interference

(C) doppler effect”

(D) reflection

1. The charge of a photo electron is :

(A) 9.1 x 10-31 C

(B) 9.1 x 10-27 C

(C) 9.1 x 10-24 C

(D) none of these

Answer: (D) none of these

1. A photocell converts light energy into :

(A) electrical energy

(B) magnetic energy

(C) sound energy

(D) None of these

Answer: (B) magnetic energy

1. In which of the following phenomenon does light intera with matter ?

(A) diffraction

(B) polarisation

(C) dispersion

(D) photoelectric effect

1. Photoelectric effect was discovered by :

(A) Hertz

(B) Hallwaqchs

(C) Lenard

(D) MKillikan

1. Photoelectric effect can be caused by :

(A) X-rays

(B) Visible light

(C) γ-rays

(D) All of these

Answer: (D) All of these

1. β-rays are deflected in:

(A) gravitational field

(B) only in magnetic field

(C) only in electric field

(D) both in magnetic and electric fields

Answer: (D) both in magnetic and electric fields

1. The energy of a photon of wavelength λ is:

(A) hcλ

(B) hc / λ

(C) hλ / c

(D) λ / hc

Answer: (B) hc / λ

1. When light enters into glass its Wavelength :

(A) Decreases

(B) Increases

(C) Remains the same

(D) None of these

1. The energy of emitted photo electron depends upon :

(A) Intensity of light

(B) Wave length of light

(C) Work-function of metal

(D) None of these

Answer: (B) Wave length of light

1. The minimum angular momentum of electron in Hydrogen atom will be:

(A) h / π Js

(B) h / 2π Js

(C) hπ Js

(D) 2π h Js

Answer: (B) h / 2π Js

1. Life of a fossil in estimated by :

(A) carbon dating

(B) X-ray

(C) y-ray

(D) laser

Answer: (A) carbon dating