Q. 273.9( 7 Votes )

# Monochromatic rad

Answer :

Given:

Wavelength of light, λ = 640.2 nm = 640.2 × 10^{-9}m

Stopping potential, V_{0} = 0.54 V

Let frequency of light = v

Work function, Φ_{0} is given by,

Φ_{0} = hv-eV_{s}

Φ_{0} = …(1)

Where,

h = Planck’s constant = 6.6 × 10^{-34}Js

c = speed of light = 3 × 10^{8}m

λ = wavelength of light

e = charge on each electron = 1.6 × 10^{-19}C

Φ_{0} =

Φ_{0} = 2.229 × 10^{-19}J or 1.39 eV

Wavelength of radiation emitted by iron, λ’ = 427.2 nm

λ’ = 4.27.2 × 10^{-9}m

The new stopping potential can be found using equation (1),

Let new stopping potential = v’

By putting the values in equation (1) we get,

Φ_{0} =

→

→

→ v’ = 1.5 eV

Therefore, the new stopping potential is 1.5 eV.

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