Home / Practice / Class 12 / Physics / Dawn of modern physics
Dawn of modern physics
Written by Dr. Hamza Farooq (Physics)
8 Class 12 Physics questions with answers and explanations.
Printable worksheet with answer key
All questions with answers
-
In the photoelectric effect, the maximum kinetic energy of emitted electrons depends on the:
- 1 Frequency of light
- 2 Area of metal
- 3 Time of exposure
- 4 Intensity of light
Show answer
Correct answer: Frequency of light
KE max = h f - work function.
Report a mistake
-
The energy of a photon is given by:
- 1 h f
- 2 h f²
- 3 h / f
- 4 f / h
Show answer
Correct answer: h f
E = h f.
Report a mistake
-
de Broglie wavelength is:
- 1 p / h
- 2 h / p
- 3 h / E
- 4 h p
Show answer
Correct answer: h / p
wavelength = h / momentum.
Report a mistake
-
Compton scattering shows that light behaves as:
- 1 Particles
- 2 Only waves
- 3 Neutral rays
- 4 Sound
Show answer
Correct answer: Particles
It treats a photon as a particle with momentum.
Report a mistake
-
Einstein's famous mass energy relation is:
- 1 E = m c
- 2 E = m c²
- 3 E = m² c
- 4 E = c / m
Show answer
Correct answer: E = m c²
E = m c².
Report a mistake
-
The minimum frequency of light needed to emit photoelectrons is the:
- 1 Beat frequency
- 2 Threshold frequency
- 3 Resonant frequency
- 4 Critical frequency
Show answer
Correct answer: Threshold frequency
Below it no emission occurs.
Report a mistake
-
Heisenberg's uncertainty principle says we cannot know exactly both the position and the:
- 1 Charge
- 2 Momentum
- 3 Colour
- 4 Mass
Show answer
Correct answer: Momentum
The product of the uncertainties has a minimum.
Report a mistake
-
Pair production needs a photon of energy at least:
- 1 13.6 eV
- 2 1.02 MeV
- 3 931 MeV
- 4 0.51 MeV
Show answer
Correct answer: 1.02 MeV
It must supply the rest mass of an electron and a positron.
Report a mistake