Question

Two beams, one of red light and the other of blue light, of the same intensity are incident on a metallic surface to emit photoelectrons. Which emits electrons of greater frequency?

(a) Both

(b) Red light

(c) Blue light

(d) Neither

This question was posed to me in class test.

This interesting question is from Einstein’s Photoelectric Equation : Energy Quantum of Radiation in division Dual Nature of Radiation and Matter of Physics – Class 12

Answer 1

The correct answer is (c) Blue light

For explanation I would say: From Einstein’s photoelectric equation, we have

\(\frac {1}{2}\) mv^2 = h(v – v0).

Since the frequency of blue light is greater than that of the red light, blue light emits electrons of greater kinetic energy.