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A point source S of light is emitting a ...

A point source `S` of light is emitting a power `P`. A sphere of radius `r` is situated at a distance `R` from source `S( r lt lt R)`, has a mass `M` and specific heat capacity `C`. The time in which temperature of sphere rises by `theta^(@)C` is

A

`(R^(2)MCtheta)/(Pr^(2))`

B

`(2R^(2)MCtheta)/(Pr^(2))`

C

`(3R^(2)MCtheta)/(Pr^(2))`

D

`(4R^(2)MCtheta)/(Pr^(2))`

Text Solution

Verified by Experts

`I_(R )=(P)/(4piR^(2))rArr"Power"=(P)/(4piR^(2))xx2pir^(2)=(pr^(2))/(2R^(2))`
Now, `(Pr^(2))/(2R^(2))xxt=MCtheta`
`T=(2R^(2)MCtheta)/(Pr^(2))`
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