Gujarati
Hindi
11.Dual Nature of Radiation and matter
medium

A beam of light of wavelength $400\,nm$ and power $1.55\,mW$ is directed at the cathode of a photoelectric cell. If only $10 \%$ of the incident photons effectively produce photoelectron, then find current due to these electrons $...........\mu A$

[given, $hc =1240\,eV - nm , e =1.6 \times 10^{-{ }^{19}\,C }$ )

A

$5$

B

$40$

C

$50$

D

$114$

(AIIMS-2015)

Solution

(c)

$\text { Energy of incident photons }=\frac{ hc }{\lambda}$
$=\frac{1240}{400}\,eV$
$=3.1\,eV$
$=4.96 \times 10^{-19}\,J$
Hence the frequency of incident photons is $\frac{1.55 \times 10^{-3}}{4.96 \times 10^{-19}}=3.125 \times 10^{15}\,Hz$
Hence the photocurrent $=e \times v$
$=50 \times 10^{-6}\,A$
$=50\,\mu A$

Standard 12
Physics

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