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
When the atoms in a sample of hydrogen like atoms are in the fourth (n = 4) orbit, how many spectral lines will be emitted in the radiation spectrum of the sample?
4
5
6
9
When ultraviolet rays are incident on metal plate,the photoelectric effect does not occur.It occurs by incidence of
infrared rays
X -rays
radiowaves
light waves
Which one of the following statements is wrong in the context of X-rays generated from an X-ray tube?
Wavelength of characteristic X-rays decreases when the atomic number of the target increases.
Cut-off wavelength of the continuous X-rays depends on the atomic number of the target.
Intensity of the characteristic X-rays depends on the electrical power given to the X-ray tube.
Cut-off wavelength of the continuous X-rays depends on the energy of the X-ray tube.
Light of wavelength 4000 angstrom is incident on a sodium surface for which the threshold wavelength of photoelectrons is 5420 angstrom. The work function is
4.58 electron volt
2.31 electron volt
1.14 electron volt
0.57 electron volt
If the wavelength of Hα line of the Balmer series of the hydrogen spectum is λ the wavelength of the
Hβ line is 7/20 λ
Least energetic spectral line of the Lyman series is 5/27 λ
Ionisation potential of hydrogen is hc/λ
All the above are true
Which of the following are thermions?
protons
electrons
photons
positrons
When an electron in the hydrogen atom jumps from the 2nd orbit to the 1st orbit, the wavelength of the radiation emitted is λ. When an electron jumps from 3rd orbit to 1st orbit, the wavelength of emitted radiation would be
Einstein's work on photoelectric effect gives support to
E = mc2
E = hν
hν = 1/2 mv2
E = h/λ
Bragg's equation will have no solution, if
λ > 2d
λ < 2d
λ < d
λ = d
