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Dual Nature of Radiation and Matter · Question 37

NEET 2013MCQEasy📈 Topic in 50% papers+4−1
1

A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance from the slit. If the speed of the electrons is increased, which of the following statements is correct ?

  1. The angular width of the central maximum will decrease.
  2. The angular width of the central maximum will be unaffected.
  3. Diffraction pattern is not observed on the screen in the case of electrons.
  4. The angular width of the central maximum of the diffraction pattern will increase.

Answer

(1) The angular width of the central maximum will decrease.

Solution

de Broglie wavelength of the electrons: = hmv

Angular width of the central maximum in single-slit diffraction: 2 = 2 a

Speed v increases ⇒ λ decreases ⇒ angular width 2 a decreases

Answer: (1)

NEET 2013

Keep practising — Dual Nature of Radiation and Matter

2

The wavelength e of an electron and p of a photon of same energy E are related by

  1. p e
  2. p 1 e
  3. p e2
  4. p e
NEET 2013
3

For photoelectric emission from certain metal the cutoff frequency is . If radiation of frequency 2 impinges on the metal plate, the maximum possible velocity of the emitted electron will be (m is the electron mass)

  1. 2h m
  2. 2 h m
  3. h (2m)
  4. h m
NEET 2013
4

A source of light is placed at a distance of 50 cm from a photo cell and the stopping potential is found to be V0. If the distance between the light source and photo cell is made 25 cm, the new stopping potential will be :

  1. V0/2
  2. V0
  3. 4V0
  4. 2V0
NEET 2013 (Karnataka)
5

The de-broglie wavelength of neutrons in thermal equilibrium at temperature T is

  1. 3.08 T A
  2. 0.308 T A
  3. 0.0308 T A
  4. 30.8 T A
NEET 2013 (Karnataka)
6

If the momentum of an electron is changed by P, then the de Broglie wavelength associated with it changes by 0.5\%. The initial momentum of electron will be

  1. 200 P
  2. 400 P
  3. P200
  4. 100 P
AIPMT 2012 (Mains)
7

Two radiations of photons energies 1 eV and 2.5 eV, successively illuminate a photosensitive metallic surface of work function 0.5 eV. The ratio of the maximum speeds of the emitted electrons is

  1. 1 : 4
  2. 1 : 2
  3. 1 : 1
  4. 1 : 5
AIPMT 2012 (Mains)
8

A 200 W sodium street lamp emits yellow light of wavelength 0.6 . Assuming it to be 25% efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is

  1. 1.5 1020
  2. 6 1018
  3. 62 1020
  4. 3 1019
AIPMT 2012 (Prelims)
9

Monochromatic radiation emitted when electron in hydrogen atom jumps from first excited to the ground state irradiates a photosensitive material. The stopping potential is measured to be 3.57 V. The threshold frequency of the material is

  1. 4 1015 Hz
  2. 5 1015 Hz
  3. 1.6 1015 Hz
  4. 2.5 1015 Hz
AIPMT 2012 (Prelims)
10

An -particle moves in a circular path of radius 0.83 cm in the presence of a magnetic field of 0.25 Wb/m2. The de Broglie wavelength associated with the particle will be

  1. 1 A
  2. 0.1 A
  3. 10 A
  4. 0.01 A
AIPMT 2012 (Prelims)
11

The threshold frequency for a photosensitive metal is 3.3 1014 Hz. If light of frequency 8.2 1014 Hz is incident on this metal, the cut-off voltage for the photoelectron emission is nearly

  1. 1 V
  2. 2 V
  3. 3 V
  4. 5 V
AIPMT 2011 (Mains)

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