Answer :

The weight of the mirror is supported by the light.

The weight of mirror =mg.

Force exerted on mirror is, as mirror is fully reflecting and 30% of light which is passed through the lens is used

From equation 1 of question 6 we can write

we light fall at angle θ on mirror

taking derivative of above equation and putting θ =0 as perpendicular it is falling we get

Where =power and =force ,c =speed of light.

we get

Force =

The force exerted by light is = .

And the power of light which is used is only 30% of original

for mirror to be in equilibrium the downward force and upward force must be equal.

The weight acting downwards = the force exerted by light

Weight acting downwards =Mg

Force exerted by light=

As only 30% of light is fall on mirror, therefore only 30% of the power is in use.

Force exerted by light=

Where M= mass,

g = acceleration due to gravity.

Putting the values,

20×× 10=2 .

Hence, power is ==100MW.

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