1.

Silver has work function of 4.7 eV when ultraviolet light of wavelength 100 nm is incident upon it, a potential of 7.7 volt is required to stop the photoelectrons from reaching the collector plate. What will be the minimum de-Broglie wavelength of photoelectrons when the wavelength of incident radiations is increased by 100% ?

Answer»

3.3 Å
5.6 Å
10 Å
12.27 Å

Solution :`7.7 = E-4.7 implies E = 12.4 eV`
When the wavelength is increased by 100% then
energy of incident photon wil be `6.2 eV` then
`K_("max") = E - 4.7 = 6.2 - 4.7 = 1.5 eV`
`:. lambda_(dB) = SQRT((150)/(V)) = sqrt((150)/(1.5))` Å = 10 Å.


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