Question

The threshold energy for photoelectric emission of electrons from a metal is 3.056x10-15 joule.

If light of 4000Ao wavelength is used, will the electrons be ejected or not?​

Answer 1

Threshold energy is the amount of energy required to remove an electron from metal surface. so, if incident energy is greater than threshold energy , electrons must be ejected and if less than threshold energy, electrons won't be ejected.

here, threshold energy , W = 3.056 × 10^-15 J

wavelength of incident light , λ = 4000 A° = 4 × 10^-7 m

using formula, E = hc/λ

here, h = 6.63 × 10^-34 Js, c = 3 × 10^8 m/s

then, E = (6.63 × 10^-34 × 3 × 10^8)/(4 × 10^-7)

= 4.9725 × 10^(-34 + 15) J

= 4.9725 × 10^-19 J

here it is clear that, E < W ( threshold energy is greater than energy of incident light) so, electrons won't be ejected.

Answer 2

Answer:

here, threshold energy , W = 3.056 × 10^-15 J

wavelength of incident light , λ = 4000 A° = 4 × 10^-7 m

using formula, E = hc/λ

here, h = 6.63 × 10^-34 Js, c = 3 × 10^8 m/s

then, E = (6.63 × 10^-34 × 3 × 10^8)/(4 × 10^-7)

= 4.9725 × 10^(-34 + 15) J

= 4.9725 × 10^-19 J

here it is clear that, E < W ( threshold energy is greater than energy of incident light) so, electrons won't be ejected

Explanation: