Question

The number of photons falling per second on a completely darkened plate to produce a force of $6.62\times {10}^{-5}$N is 'n'. If the wavelength of the light falling is $5\times {10}^{-7}$m, then $n=$______$\times {10}^{22}$. $(h=6.62\times {10}^{-34}J-s)$

• A. $1$
• B. $5$
• C. $0.2$
• D. $3.3$

Answer 1

The correct option is B $5$

$P=\frac{n}{t}.\frac{hc}{\lambda }$

$Fc=\frac{n}{t}.\frac{hc}{\lambda }$

$\frac{n}{t}=\frac{f\lambda }{n}$

$\frac{n}{t}=\frac{6.62\times {10}^{-5}\times 5\times {10}^{-7}}{6.62\times {10}^{-34}}$

$=5\times {10}^{2}2V$