Question

A light bulb radiates 110 nW of single-frequency sinusoidal electromagnetic waves uniformly in all directions. Calculate the average intensity of the light from this bulb at a distance of 50 mm

Answer 1

The intensity of the light from the bulb would be

3.501 x
`10^(-6)` W/
`m^(2)`

Step-by-step explanation:

Given

The Power = 110 n W = 110 x
`10^(-9)` W

the distance r = 50 mm = 50 /1000 = 0.05 m

The intensity can be obtained with the relationship below;

I = Power/area ......1

The area of the sphere would be used in this case since the bulb is spherical; A=4π
`r^(2)`

Putting it into equation 1, we have;

I = P/ 4π
`r^(2)`

I = 110 x
`10^(-9)` / 4 x π x
`0.05^(2)`

I = 3.501 x
`10^(-6)` W/
`m^(2)`

Therefore the intensity of the light from the bulb would be

3.501 x
`10^(-6)` W/
`m^(2)`