RAS question
Photoelectric effect, explained by Einstein, proved that light has:
Correct answer: (C) Particle nature (photons).
Einstein's explanation of the photoelectric effect proved the particle nature of light, with light behaving as discrete photons.
Explanation
The photoelectric effect showed that light cannot be understood as only a continuous wave in this context. Einstein explained it in 1905 by treating light as discrete packets, later called photons, whose energy depends on frequency, expressed as E=hnu. That is why the effect is taken as evidence for the particle nature of light, while still complementing the already known wave nature of light. The NCERT Physics syllabus places this under "Dual Nature of Matter and Radiation" and specifically links the photoelectric effect and Einstein's photoelectric equation with the particle nature of light. This is also the work for which Einstein received the 1921 Nobel Prize in Physics.
Why the other options are wrong
- (A) The photoelectric effect is not evidence that light lacks both wave and particle nature; Einstein's explanation specifically supports light behaving as particles in this phenomenon.
- (B) Only wave nature is wrong because the given effect is classically important precisely for showing particle behaviour through photons, not merely wave behaviour.
- (D) Magnetic nature only is unrelated to Einstein's photoelectric explanation, which concerns energy packets of light and their frequency-dependent energy.
Concept
This tests the Class XII/RAS science concept of dual nature of radiation, especially how one experiment can establish particle behaviour while other optics topics retain wave behaviour. It recurs in RAS because photoelectric effect is a compact way to test modern physics, Nobel-linked scientific history, and conceptual clarity together.