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Physics Question on Reflection Of Light By Spherical Mirrors

A small object at rest, absorbs a light pulse of power 20 mW20 \,mW and duration 300 ns300\, ns. Assuming speed of light as 3×108 m/s3 \times 10^8 \,m / s, the momentum of the object becomes equal to :

A

2×10−17kg m/s2 \times 10^{-17} kg \,m / s

B

1×10−17kg m/s1 \times 10^{-17} kg \,m / s

C

3×10−17kg m/s3 \times 10^{-17} kg\, m / s

D

0.5×10−17kg m/s0.5 \times 10^{-17} kg \,m / s

Answer

2×10−17kg m/s2 \times 10^{-17} kg \,m / s

Explanation

Solution

Momentum =C Energy ​
=C Power × time ​
=3×108m/s(20×10−3w)(300×10−9s)​
=2×10−17kg−m/s