Gases begin to conduct electricity at low pressure because
at low pressures gases turn to plasma
colliding electrons can acquire higher kinetic energy due to increased mean free path leading to ionisation of atoms
atoms break up into electrons and protons
the electrons in atoms can move freely at low pressures
The figure shows a plot of photo current versus anode potential for a photo sensitive surface for three different radiations. Which one of the following is a correct statement ?
Curves a and b represent incident radiations of different frequencies and different intensities
Curves a and b represent incident radiations of same frequency but of different intensities
Curves b and c represent incident radiations of different frequencies and different intensities
Curves b and c represent incident radiations of same frequency having same intensity
The nature of ions knocked out from hot surfaces is
protons
electrons
neutrons
nuclei
A radio transmitter operates at a frequency 880 KHz and a power of 10 kW. The number of photons emitted per second is
1.72 × 1031
1.327 × 1025
1.327 × 1037
1.327 × 1045
A particle of mass 1 mg has the same wavelength as an electron moving with a velocity of 3 × 106 ms-1 . The velocity of the particle is (mass of electron = 9.1 × 10-31 kg)
2.7 × 10-18 ms-1
9 × 10-2 ms-1
3 × 10-31 ms-1
2.7 × 10-21 ms-1
In X-rays diffraction experiment distance between atomic lattice planes of diffraction grating is 2.8 ×10-10 m, then the maximum wavelength of X-rays (in metre) is
2.5
5.6 × 10-10
4 × 10-10
4.6 × 10-10
Kinetic energy of an electron which is accelerated in a potential difference of 100 V is
1.6 × 10-17 J
1.6 × 10-19 J
1.6 × 10-21 J
1.6 × 10-25 J
A photoelectric cell is illuminated by a point source of light 1 m away. When the source is shifted to 2 m, then
each emitted electron carries half the initial energy
number of electrons emitted is a quarter of the initial number
each emitted electron carries one quarter of the initial energy
number of electrons emitted is half the initial number
The work function of a surface of a photosensitive material is 6.2 eV. The wavelength of the incident radiation for which the stopping potential is 5 V lies in the
ultraviolet region
visible region
infrared region
X-ray region
The number of photoelectrons emitted for light of a frequency v (higher than the threshold frequency v0 ) is proportional to
v - v0
threshold frequency (v0 )
intensity of light
frequency of light (v)
