The threshold wavelength for photoelectric emission from a material… | JEE Main 2023 (29 Jan, Shift 1)

Q74JEE Main 2023 · 29 JAN · SHIFT 1Easy

Photoelectric Effect: Einstein's Equation

The threshold wavelength for photoelectric emission from a material is 5500 $\mathring{A}$ . Photoelectrons will be emitted, when this material is illuminated with monochromatic radiation from a A. 75 W infra-red lamp

B. 10 W infra-red lamp

C. 75 W ultra-violet lamp

D. 10 W ultra-violet lamp

Choose the correct answer from the options given below:

Show answer and solution

Answer: (c)

Emission needs $\lambda < \lambda_0 = 5500\,\mathring{A}$ , whatever the intensity (power) of the lamp.
Infra-red has $\lambda > 7000\,\mathring{A} > \lambda_0$ : no emission from A or B, even at 75 W.
Ultra-violet has $\lambda < 4000\,\mathring{A} < \lambda_0$ : emission from both C and D, even at 10 W.
So the answer is (c) C and D only.

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Photoelectric Effect: Einstein's Equation question from JEE Main 2023 (29 Jan, Shift 1)

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