Question

Question 2.12 Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 Å. Calculate threshold frequency (v0) and work function (W0) of the metal.

Class XI Structure of Atom Page 65

Answer 1

Given,
Threshold wavelength ( λ₀ ) = 6800 A°
= 6800 × 10^-10 m = 6.8 × 10^-7 m

Threshold frequency ( v₀ ) = c/λ₀ = speed of light / threshold wavelength
= 3 × 10^8/6.8 × 10^-7 = 4.41 × 10¹⁴ Hz

we know,
Work function ( W₀ ) = hv₀
= 6.626 × 10^-34 Js × 4.41 × 10¹⁴ Hz
= (6.626 × 4.41 ) × 10^(-34 + 14) J
= 29.22 × 10^-20 J
= 2.922 × 10^-19 J