A metal has a threshold wavelength of 6000 A o . Calculate the threshold frequency and the work function of the metal in e V .

Given the threshold wavelength= λ = 6000 × 10 - 10 m The wavelength and frequency is related by the relation ν = c λ where c = velocity of the light.Substituting the values in the formula, we have ν = 3 × 10 8 6000 × 10 - 10 = 5 × 10 14 Hz The work function will be the energy corresponding to this wave length, which is given by W = hν = 6 . 63 × 10 - 34 × 5 × 10 14 1 . 6 × 10 - 19 = 2 . 06 eV

Photoelectric threshold frequency of an alkali metal is 5 . 0 × 10 14 Hz . Calculate the work function of this metal.

Given threshold frequency ν 0 = 5 . 0 × 10 14 Hz The work function of a metal is given by ϕ 0 = h ν 0 , where h = Planck's constant. Substituting the values ϕ 0 = 6 . 62 × 10 - 34 × 5 × 10 14 = 33 . 1 × 10 - 20 J or ϕ 0 = 33 . 1 × 10 - 20 J 1 . 6 × 10 - 19 = 2 . 06 e V

E M B I B E

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 14

MEDIUM

12th ICSE

IMPORTANT

Earn 100

A photon ejects an electron of negligible kinetic energy from a metal surface. If the threshold frequency for the surface be $4.6 \times 10^{14} Hz$ , Calculate the energy of the incident photon in electron-volt.

Important Questions on Photoelectric Effect

MEDIUM

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 15

A metal sheet has a negative charge of

11.2 nC (1 nC = 10^{- 9} C)

. How many photons of ultraviolet light are required to completely discharge the sheet by photoelectron ejection? What minimum amount of energy must be absorbed by the sheet to effect this discharge? The threshold frequency of the metal is