Question

Photo electrons with a maximum speed of 7 × 10⁵ m/sec are emitted from a metal surface when light of frequency 8 × 10¹⁴ Hz falls on it. Calyculate the threshold frequency of the surface.

Answer 1

or 1/2 × 9.1 × 10^–31 × (7 × 10⁵ )² = 6.625 × 10^–34 (8 × 10¹⁴ – f ₀ )

∴ f₀ = 4.635 × 10¹⁴ Hz