A small object at rest, absorbs a light pulse of power 20   mW and duration 300   ns . Assuming…

A small object at rest, absorbs a light pulse of power 20 mW and duration 300 ns. Assuming speed of light as 3 × 108 m s-1. The momentum of the object becomes equal to :
  1. 0.5×10-17 kg m s-1
  2. 2×10-17 kg m s-1
  3. 3×10-17 kg m s-1
  4. 1×10-17 kg m s-1

Solution

Momentum p=EnergyESpeed of lightc

=Power×timec

=20×10-3W300×10-9s3×108 m s-1

=2×10-17 kg m s-1

As momentum is conserved, therefore momentum of object will be 2×10-17 kg m s-1.

Asked in: JEE Main 2023 (30 Jan Shift 1)

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