Question

1)The minimum frequency of light needed to eject electrons from a metal is called the threshold frequency, ν0. Find the minimum energy needed to eject electrons from a metal with a threshold frequency of 4.55 × 1014 s–1.

2)With what maximum kinetic energy will electrons be ejected when this metal is exposed to light with a wavelength of λ = 265 nm?

Answer 1

we know

E = E⁰ + K.E

E⁰ = threshold energy

K.E is kinetic energy

hν = hν₀ + K.E

1.

minimum energy needed to eject electrons from a metal = hν₀ = 6.625 * 10^-34 J.s * 4.55 * 10¹⁴.s^-1

                                                                                                                  = 30.14375 * 10^-20J

2.

K.E = hν - hν₀

      = hc / Λ - (30.14375 * 10^-20J)

      = [(6.625 * 10^-34J.s * 3*10⁸m/s) / 265 * 10^-9m] - (30.14375 * 10^-20J)

      = 44.857 * 10^-20 J