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A $1.5 \mathrm{KW}$ (kilo-watt) laser beam of wavelength $6400 Å$ is used to levitate a thin aluminium disk of same area as the cross section of the beam. The laser light is reflected by the aluminium disk without any absorption. The mass of the foil is close to
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The correct answer is:
$10^{-}{ }^{6} \mathrm{~kg}$
$\begin{array}{l}
\mathrm{F}=\frac{2 \mathrm{P}}{\mathrm{C}} \\
\mathrm{mg}=\frac{2 \times 1.5 \times 10^{3}}{3 \times 10^{8}} \\
\mathrm{~m}=10^{-6} \mathrm{~kg}
\end{array}$
\mathrm{F}=\frac{2 \mathrm{P}}{\mathrm{C}} \\
\mathrm{mg}=\frac{2 \times 1.5 \times 10^{3}}{3 \times 10^{8}} \\
\mathrm{~m}=10^{-6} \mathrm{~kg}
\end{array}$
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