Dual Nature of Radiation and Matter · Question 40

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

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

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

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

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

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

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

Photoelectric emission occurs only when the incident light has more than a certain minimum

1. power
2. wavelength
3. intensity
4. frequency

Light of two different frequencies whose photons have energies 1 eV and 2.5 eV respectively illuminate a metallic surface whose work function is 0.5 eV successively. Ratio of maximum speeds of emitted electrons will be

1. 1 : 4
2. 1 : 2
3. 1 : 1
4. 1 : 5

Electrons used in an electron microscope are accelerated by a voltage of 25 kV. If the voltage is increased to 100 kV, then the de Broglie wavelength associated with the electrons would

1. increase by 2 times
2. decrease by 2 times
3. decrease by 4 times
4. increase by 4 times