Einstein was honoured with Nobel Prize for ............

The answer is A) Photoelectric effect. Einstein received the 1921 Nobel Prize (presented in 1922) for services to theoretical physics, and especially for his discovery of the law of the photoelectric effect. The citation names this work and not relativity, which is why the prize is a frequent exam trap.

• B) Theory of Specific Heats is wrong. His 1907 model of the specific heat of solids was important, but it was not the basis of the Nobel citation.
• C) Special Theory of Relativity is wrong. Relativity (1905) was never cited, partly because the committee found it hard to verify experimentally at the time.
• D) Bose-Einstein Statistics is wrong. This was developed in 1924-25 with Satyendra Nath Bose, and it was not the Nobel-winning work.

The core concept is the quantum of light: light energy comes in packets (photons), and E = hf explains why emission depends on frequency and not intensity. This is a cornerstone of quantum theory and underlies photocells and solar cells, which is a useful Mains link for science and technology.

Trap: Aspirants pick relativity because it is the most famous Einstein theory. The Nobel was for the photoelectric effect.