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Ultraviolet light of wavelength 280 nm i...

Ultraviolet light of wavelength 280 nm is used in an
experiment on photoelectric effect with lithium
`( varphi = 2.5 eV)` cathode. Find (a) the maximum kinetic
energy of the photoelectrons and (b) the stopping
potential.

Text Solution

Verified by Experts

(a) The maximum kinetic energy is
` K_max = (hc/lambda)- varphi. `
`= (1242 eV nm/ 280 nm)- 2.5 eV. `
` = 4.4 eV - 2.5 eV = 1.9eV. `
(b) Stopping potential V is given by
` eV= K_max`
` or, V=(K_max)/e = 1.9 eV/e = 1.9 V.`
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