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The threshold wavelength of tungsten is 2300 angstroms. If ultra violet light of wavelength 1800 angstroms is incident on it,then what would be the maximum kinetic energy of photoelectrons?

The threshold wavelength of tungsten is 2300 angstroms. If ultra violet light of wavelength 1800 angstroms is incident on it,then what would be the maximum kinetic energy of photoelectrons?
 
 

Grade:12

1 Answers

Arun
25757 Points
3 years ago
wavelength(λ) of UV light= 188 nm 
Energy of incident rays = hc/λ (h=planks constant,c=speed of light) =1242 eV-nm/188 nm=6.606 eV 
Threshold λ=230 nm 
Threshold energy=work function ( Φ )=1242eV-nm/230 nm= 5.4 eV. 
By einstein photo-electric effect, 

Energy Incident=Φ + Maximum K.E. 

Thus maximum kinetic energy of emitted electrons would be=6.606 - 5.4 = 1.206 eV.
 
RegaRds
Arun

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