Practice portal › Dual Nature of Matter and Radiation › Einstein's Photoelectric Equation and Work Function
Asked in JEE Main 29th Jan 1st Shift 2023 · Threshold frequency and wavelength
Given: λ₀=5500 A=550 nm, in the green.
Emission needs λ<λ₀, that is a photon energy above φ=1240/550=2.25 eV.
Infra-red lies beyond 700 nm, so it is below threshold whatever the lamp power.
Ultra-violet lies below 400 nm, comfortably above threshold.
The lamp power sets how many electrons come out, never whether any do.
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