Question

Ultraviolet light of wavelength 2271 Å from a 100 W mercury source irradiates a photocell made of molybdenum metal. If the stopping potential is −1.3 V, estimate the work function of the metal. How would the photo-cell respond to a high intensity ( 105 W m⁻²) red light of wavelength 6328 Å produced by a He-Ne laser?

Answer 1

Wavelength of ultraviolet light, λ = 2271 Å = 2271 × 10⁻¹⁰ m
Stopping potential of the metal, V0 = 1.3 V
Planck’s constant, h = 6.6 × 10⁻³⁴ J
Charge on an electron, e = 1.6 × 10⁻¹⁹ C

Since ν0> νr, the photocell will not respond to the red light produced by the laser.