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A pulse of light of duration 10^(-6) s i...

A pulse of light of duration `10^(-6)` s is absorbed completely by a small object initially at rest. If the power of the pulse is `60 xx 10^(-3)` W, calculate the final momentum of the object.

Text Solution

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Given: Duration of absorption of light t = `10^(-6)` s.
power of the pulse, P = 6`xx 10^(-3) W`
To find :
The final momentum of the object, `Delta`p = ?
formula:
`Delta`p = `(U)/(c ) = ("energy")/("velocity of light in vacuum")`
Solution :
Energy = power `xx` time
= `60 xx 10^(-3) xx 10^(-6)`
`U = 60 xx 10^(-9)`
`Delta P = (60 xx 10^(-9))/(3 xx 10^(8)) = 20 xx 10^(-17) " kg " m s^(-1)`
`Delta p = 20 xx 10^(-17) " kg m"s^(-1)`
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