JEE Main 2026 Physics question
For a certain metal, when monochromatic light of wavelength λ is incident, the stopping potential for photoelectrons is 3V₀. When the same metal is illuminated by light of wavelength 2λ, then the stopping potential becomes V₀. The threshold wavelength for photoelectric emission for the given metal is αλ. The value of α is .
Answer: (B)
Solution
hc/λ − φ = 3eV₀ and hc/(2λ) − φ = eV₀. Subtracting: hc/(2λ) = 2eV₀ ⇒ hc/λ = 4eV₀ and φ = eV₀. The threshold wavelength is hc/φ = 4λ.