1.

A photoelectric surface is illuminated successively by monochromatic ligth of wavelength lambda and (lambda)/(2). If the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function at the surface of material is........................

Answer»

`(hc)/(lambda)`
`(2hc)/(lambda)`
`(hc)/(3 lambda)`
`(hc)/(2 lambda)`

SOLUTION :`KE_(1) = (hc)/(lambda) - phi""…(1)`
`3KE_(1) = (2hc)/(lambda) - phi`
`KE_(1) = (2hc)/(3 lambda) - (phi)/(3)""…(2)`
Equating (1) and (2)
`(hc)/(lambda) - phi""= (2hc)/(3 lambda) - (phi)/(3)`
`(hc)/(3 lambda) = (2 phi)/(3) RARR phi = (hc)/(2 lambda)`


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