Question

When a piece of metal is illuminated by monochoromatic light of wavelength λ , then the stopping potential for photoelectric current is 2.5 eV. When the same surface is illuminated by light of wavelength 1.5 λ , then the stopping potential is observed to have a value V_S. From this data the threshold wavelength of photoelectric emission is 

(1) 2.5 λ 

(2) 2.25 λ 

(3) 2.75 λ 

(4) 2.00 λ

Answer 1

Correct option : (2) 2.25 λ

Explanation :

From Einstein’s photoelectric equation we have eV_s = hv - ω₀ = hc/λ - ω₀ 

so that we can write from the data given in the question