If 2.5 $\times$ 10$-$6 N average force is exerted by a light wave on a non-reflecting surface of 30 cm2 area during 40 minutes of time span, the energy flux of light just before it falls on the surface is ___________ W/cm2. (Round off to the Nearest Integer)
(Assume complete absorption and normal incidence conditions are there)
Answer (integer)
25
Solution
Pressure = ${{Intensity} \over C}$ (for absorbing surface)<br><br>I = P $\times$ C<br><br>I = ${{2.5 \times {{10}^{ - 6}}} \over {30c{m^2}}}$ N $\times$ 3 $\times$ 10<sup>8</sup> m/s<br><br>I = 25 W/cm<sup>2</sup>
About this question
Subject: Physics · Chapter: Electromagnetic Waves · Topic: Properties of EM Waves
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