An electron of mass m and charge e is accelerated from rest through a potential difference of V volt in vacuum. Its final speed will be
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
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
In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential V and then made to describe semicircular paths of radius R using a magnetic field B. If V and B are kept constant, the ratio will be proportional to
R2
R
When light of wavelength 300nm (nanometer) falls on a photoelectric emitter, photoelectrons are liberated. For another emitter, however, light of 600 nm wavelength is sufficient for creating photoemission, what is the ratio of the work functions of the two emitters ?
1 : 2
2 : 1
4 : 1
1 : 4
In the phenomenon of electric discharge through gases at low pressure, the coloured glow in the tube appears as a result of
excitation of electrons in the atoms
collision between the atoms of the gas
collisions between the charged particles emitted from the cathode and the atoms of the gas
collision between different electrons of the atoms of the gas
The cathode of a photoelectric cell is changed such that the work function changes from W1 to W2 ( W2 > W1 ). If the current before and after changes are I1 and I2, all other conditions remaining unchanged, then (assuming hv > W2 )
I1 = I2
I1 < I2
I1 > I2
I1< I2< 2I1
The energy of a photon of light is 3 eV. Then the wavelength of photon must be
4125 nm
412.5 nm
41250 nm
4 nm
If the threshold wavelength for a certain metal is 2000Å, then the work function of the metal is
6.2 J
6.2 eV
6.2 MeV
6.2 keV
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
