Light of frequency 7.21 × 10¹⁴ Hz is incident on a metal. Electrons with maximum speed 6.0 × 10⁵ m s⁻¹ are emitted. Find the threshold frequency.
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Light of frequency 7.21 × 10¹⁴ Hz is incident on a metal. Electrons with maximum speed 6.0 × 10⁵ m s⁻¹ are emitted. Find the threshold frequency.

G1 Physics · Accepted Answer

Einstein equation gives hν = φ + ½mv², so ν₀ = ν − mv²/(2h). Substitution gives ν₀ ≈ 4.73 × 10¹⁴ Hz. Correct answer: A.