Q155 / 160 · AP EAMCET 2019 (20 Apr Shift 2) · Physics
A lamp delivers a luminous flux of $100 \mathrm{~W}$ to an absorber of area $\mathrm{l} \mathrm{cm}^2$. The force due to radiation pressure is
- A$3.3 \times 10^{-4} \mathrm{~N}$
- B$16.5 \times 10^{-7} \mathrm{~N}$
- C$3.3 \times 10^{-6} \mathrm{~N}$
- Correct answerD$3.3 \times 10^{-7} \mathrm{~N}$
Solution
$\because$ Force $=$ Rate of change of linear momentum
$$
F=\frac{d p}{d t}=\frac{d}{d t}\left(\frac{v}{c}\right)=\frac{1}{c} \frac{d v}{d t}
$$
where, $v=$ electromagnetic wave energy.
$$
\begin{aligned}
& F=\frac{I}{c}=\frac{100}{3 \times 10^8}=33.3 \times 10^{-8} \mathrm{~N} \\
& F=3.3 \times 10^{-7} \mathrm{~N}
\end{aligned}
$$
$[(\because I=100$ watt, given $]$
Hence, the correct answer is option: 'D'.