J J Thomson's cathode ray tube experiment demonstrated that
the e/m of electrons is greater than the e/m of protons
the e/m ratio of the cathode ray particles changes when a different gas is placed in the discharge tube
cathode rays are streams of negatively charged ions
all the mass of an atom is essentially in the nucleus
Ultraviolet radiation of 6.2eV falls on an aluminium surface. KE of fastest electron emitted is (work function = 4.2 eV)
3.2 × 10-21 J
3.2 × 10-19 J
7 × 10-25 J
9 × 10-32 J
A 5 W source emits monochromatic light of wavelength 5000Å. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. When the source is moved to a distance of 1.0 m, the number of photoelectrons liberated will be reduced by a factor of
4
8
16
2
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
According to Einstein's photoelectric equation, the graph between the kinetic energy of photoeletrons ejected and the frequency of incident radiation is
The following particle are moving with the same velocity, then maximum de-Broglie wavelength will be for
proton
α-particle
neutron
β-particle
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
Monochromatic light of frequency 6.0×1014 Hz is produced by a laser. The power emitted is 2× 10-3 W. The number of photons emitted, on the average, by the source per second is
5 × 1015
5 × 1016
5 × 1017
5 × 1014
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
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