Dual Nature of Radiation and Matter · Question 46

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

In photoelectric emission process from a metal of work function 1.8 eV, the kinetic energy of most energetic electrons is 0.5 eV. The corresponding stopping potential is

1. 1.8 V
2. 1.3 V
3. 0.5 V
4. 2.3 V

In the Davisson and Germer experiment, the velocity of electrons emitted from the electron gun can be increased by

1. increasing the potential difference between the anode and filament
2. increasing the filament current
3. decreasing the filament current
4. decreasing the potential difference between the anode and filament

A radioactive nucleus of mass M emits a photon of frequency and the nucleus recoils. The recoil energy will be

1. Mc2 - h
2. h2 2/2Mc2
3. zero
4. h

When monochromatic radiation of intensity I falls on a metal surface, the number of photoelectrons and their maximum kinetic energy are N and T respectively. If the intensity of radiation is 2I, the number of emitted electrons and their maximum kinetic energy are respectively

1. N and 2T
2. 2N and T
3. 2N and 2T
4. N and T

The electron in the hydrogen atom jumps from excited state (n = 3) to its ground state (n = 1) and the photons thus emitted irradiate a photosensitive material. If the work function of the material is 5.1 eV, the stopping potential is estimated to be (the energy of the electron in nth state En = - 13.6n2 eV)

1. 5.1 V
2. 12.1 V
3. 17.2 V
4. 7 V

A source S1 is producing 1015 photons per second of wavelength 5000 A. Another source S2 is producing 1.02 1015 photons per second of wavelength 5100 A. Then, (power of S2)/(power of S1) is equal to

1. 1.00
2. 1.02
3. 1.04
4. 0.98