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About 5% of the power of a 100 W light b...

About 5% of the power of a 100 W light bulb is converted to visible radiation. What is the average intensity of visible radiation
a. at a distance of 1m from the bulb
b. at a distance of 10m
Assume that the radiation is emitted isotropically and neglect reflection.

Text Solution

Verified by Experts

a. `A=4pi r^(2)=4xx3.14xx1^(2)m^(2)`
`I=("Power")/("Area")=(100xx 5//100)/(4xx3.14xx1^(2))=0.4 Wm^(-2)`
b. `I=(100xx 5//100)/(4xx3.14xx10^(2))=0.004 Wm^(-2)`
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