Selected MCQ

Current Question
The Doppler effect for light leads to redshift when:
  • A. Source approaches observer
  • B. Source moves away
  • C. Observer moves toward source
  • D. Wavelength decreases
Correct Answer: B
Explanation:
Receding source increases wavelength (redshift).
Related Question 1
In the photoelectric effect, increasing light intensity at fixed frequency above threshold increases:
  • A. Maximum kinetic energy of emitted electrons
  • B. Number of emitted electrons per unit time
  • C. Threshold frequency
  • D. Work function
Correct Answer: B
Explanation:
Intensity raises photon flux, hence emission rate, but not per-electron maximum energy.
Related Question 2
Which symmetry leads to conservation of energy (Noether’s theorem)?
  • A. Spatial symmetry
  • B. Time translation symmetry
  • C. Rotational symmetry
  • D. Gauge symmetry
Correct Answer: B
Explanation:
Invariance under time translation implies energy conservation.
Related Question 3
Which phenomenon bends light?
  • A. Reflection
  • B. Refraction
  • C. Diffraction
  • D. Interference
Correct Answer: B
Explanation:
Refraction changes direction in medium.
Related Question 4
The cosmological redshift is due to:
  • A. Doppler motion only
  • B. Expansion of space
  • C. Gravitational collapse
  • D. Magnetic fields
Correct Answer: B
Explanation:
Light stretches as universe expands.
Related Question 5
Which plant pigment absorbs light?
  • A. Chlorophyll
  • B. Hemoglobin
  • C. Keratin
  • D. Melanin
Correct Answer: A
Explanation:
Chlorophyll captures light energy.