JEE MAIN - Physics (2020 - 3rd September Morning Slot - No. 14)
When the wavelength of radiation falling on a metal is changed from 500 nm to 200 nm, the
maximum kinetic energy of the photoelectrons becomes three times larger. The work function of
the metal is close to :
1.02 eV
0.81 eV
0.61 eV
0.52 eV
Explanation
K1 = $${{hc} \over {500}} - {\phi _0}$$
K2 = $${{hc} \over {200}} - {\phi _0}$$
$$ \because $$ K2 = 3K1
$$ \Rightarrow $$ $$3\left[ {{{hc} \over {500}} - {\phi _0}} \right] = \left[ {{{hc} \over {200}} - {\phi _0}} \right]$$
$$ \Rightarrow $$ $$\phi $$0 = 0.61 eV
K2 = $${{hc} \over {200}} - {\phi _0}$$
$$ \because $$ K2 = 3K1
$$ \Rightarrow $$ $$3\left[ {{{hc} \over {500}} - {\phi _0}} \right] = \left[ {{{hc} \over {200}} - {\phi _0}} \right]$$
$$ \Rightarrow $$ $$\phi $$0 = 0.61 eV
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