Which of the following radiations is least penetrating?
α - particles
β - particles
x - rays
γ - radiations
Speed of beta particle is
107 m/s
2.7 x 108 m/s
3 x 108 m/s
108 m/s
The maximum number of electrons in a shell of number 'n' is given by.
2n
22n
2n2
n3
Why is the cathode ray tube evacuated to a low pressure?
To avoid the effect of external electric field on the beam of electrons.
To increase the energy of the beam of electrons.
To avoid collisions of electrons with the air molecules
To increase the rate of emission.
The rate of emission of electrons from a surface does not depend upon:
the temperature of surface
the shape of metal surface
the nature of the metal surface
the surface area of metal
Which of the following is most harmful for the human being :
Light rays
Beta particles
Gamma rays
Alpha particles
The minimum amount of energy required to emit electrons from a metal surface is called the:
cohesive energy
work function
ionisation energy
dissociation energy
Which of the following radiations suffers maximum deflection in magnetic field?
β - particle
Which of the following metals cannot be used to coat tungsten inorder to reduce its work function?
Magnesium
Strontium
Cesium
Barium
Which substance is most suitable to be used as an electron emitter?
Na
Ni
W
K
