Question

If the critical wavelength for producing photoelectric effect is 2000A then what is the wavelength of light required to produce photoelectrons with double the kinetic energy of those produced by the light of wavelength 1500A

Answer 1

Answer:

Explanation:

Let :

Critical wavelength = w°

Wavelength when kinetic energy is normal = w₁

When K. E is doubled = w₂

K. E₁ = 1 / w₁ — 1/ w°

K. E₂ = 2K.E₁

K. E₂ = 1 / w₂ — 1 / w°

1 / w₂ — 1 / w° = 2 / w₁ —2 / w°

1 / w₂ = 2 / w₁ — 1 / w°

Doing the substitution :

1 / w₂ = 2 / 2200 — 1/ 2600

1 / w₂ = (2600 — 1100) / 2860000

1 / w₂ = 1500 / 2860000

w₂ = 2860000 / 1500 = 1906.667 Angstroms