A totally reflecting small plane mirror place | vedclass

Name: Exam Paper Generator | JEE NEET Paper Generator | Vedclass
Brand: Vedclass
Rating: 5 (35 reviews)

Question

(B) For a perfectly reflecting mirror,the force $F$ exerted by a beam of light with power $P_{mirror}$ is given by:$F = \frac{2 P_{mirror}}{c}$For the

Vedclass · Accepted Answer

$100$

Vedclass · Answer

(B) For a perfectly reflecting mirror,the force $F$ exerted by a beam of light with power $P_{mirror}$ is given by:$F = \frac{2 P_{mirror}}{c}$For the mirror to be in equilibrium,the radiation force must balance its weight:$F = mg$$\frac{2 P_{mirror}}{c} = mg$$P_{mirror} = \frac{mgc}{2}$Given $m = 20 \, g = 0.02 \, kg$,$g = 10 \, m/s^2$,and $c = 3 	imes 10^8 \, m/s$:$P_{mirror} = \frac{0.02 	imes 10 	imes 3 	imes 10^8}{2} = 0.01 	imes 3 	imes 10^8 = 3 	imes 10^6 \, W = 3 \, MW$Since only $30 \%$ of the total power $P_{source}$ emitted by the source reaches the mirror:$P_{mirror} = 0.30 	imes P_{source}$$3 \, MW = 0.30 	imes P_{source}$$P_{source} = \frac{3}{0.30} = 10 \, MW$Wait,re-evaluating the calculation: $P_{mirror} = \frac{0.02 	imes 10 	imes 3 	imes 10^8}{2} = 30 	imes 10^6 \, W = 30 \, MW$. Then $P_{source} = \frac{30}{0.30} = 100 \, MW$.

Similar Questions

$A$ $1.5 \,kW$ laser beam of wavelength $6400 \,\mathring A$ is used to levitate a thin aluminium disc of the same area as the cross-section of the beam. The laser light is reflected by the aluminium disc without any absorption. The mass of the foil is close to ......... $kg$.

$A$ beam of white light is incident normally on a plane surface absorbing $70 \%$ of the light and reflecting the rest. If the incident beam carries $10 \ W$ of power,the force exerted by it on the surface is

Find the compression in the spring with spring constant $K = 5 \ N/m$ which is attached to a metal plate of area $50 \ m^2$. Light of intensity $I = 40 \ MW/m^2$ is incident at an angle of $60^o$ on the metal plate,and the coefficient of reflection is $\rho = 0.5$ for the plate. (in $m$)

$A$ radiation of energy $E$ falls normally on a perfectly reflecting surface. The momentum transferred to the surface is ($C =$ velocity of light).

What is the force exerted on a surface having an area of $10\, cm^2$ due to the radiation of the Sun?

Vedclass Test Series

Exam Paper Generator

Online Exam Module