1.

Ultraviolet light of `6.2 eV` falls on an aluminium surface (work function `= 4.2 eV`). The kinetic energy (in joule) of the fastest electron emitted is approximately.A. `3 xx 10^-21`B. `3 xx 10^-19`C. `3 xx 10^-17`D. `3 xx 10^-15`

Answer» Correct Answer - B
(b) `hv = hv_0 + KE`
`KE = hv - hv_0 hv = 6.2 eV`
=`6.2 - 4.2 hv_0 = 4.2 e V`
=`2.00 xx 1.6 xx 10^-19`
`KE = 3.2 xx 10^-19 J`.


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