When ultraviolet light with a wavelength of 254 nm falls on a clean copper surface, the stopping potential necessary to stop emission of photoelectrons is 0.181 v. part a what is the photoelectric threshold wavelength for this copper surface?

The ultraviolet wavelength λ = 254nm the stopping potential of copper surface,

V₀ = 0.18W

Now the relation between threshold wavelength and stopping potential is

eV₀ = λc (1/λ - 1/λ₀)

1/λ - 1/λ₀ = eV₀/λc

1/λ₀ = 1/λ eV/λc

= 1 / 254 * 10⁻⁹m - 1.6 10⁻¹⁹C) (0.181v) / 6.625 * 10⁻³⁴ Js (3*10⁸m/s

0.00393 * 10⁹ - 0.01457*10⁷

= 0.378 * 10⁷

λ₀ = 264 * 10⁻⁹m or

264nm