About 5% of

(a) Given : Power of the bulb = 100 W

Since, 5% of the power of a 100 W light bulb is converted to visible radiation, therefore the power of visible radiation can be calculated as follows:

P’ = 5W

The average intensity of visible radiation at a distance of 1m from the bulb can be calculated by using the following formula:

⇒

⇒

⇒ I = 0.398 W/m²

(b) The average intensity of visible radiation at a distance of 10 m from the bulb can be calculated by using the following formula:

I = P’/4π d²

I =

I = 5/1256

I = 0.00398 W/m²