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

Answer:

The intensity of the light from the bulb would be

3.501 x $10^{-6}$ W/$m^{2}$

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/$m^{2}$