Question

A 40-W lightbulb is 1.7 m from a screen. What is the intensity of light incident on the screen? Assume that a lightbulb emits radiation uniformly in all directions (i.e., over 4π steradians).

Answer 1

Intensity,
`I=1.101\ W/m^2`

Step-by-step explanation:

Power of the light bulb, P = 40 W

Distance from screen, r = 1.7 m

Let I is the intensity of light incident on the screen. The power acting per unit area is called the intensity of the light. Its formula is given by :

`I=(P)/(A)`

`I=(P)/(4\pi r^2)`

`I=(40\ W)/(4\pi (1.7\ m)^2)`

`I=1.101\ W/m^2`

So, the intensity of light is
`1.101\ W/m^2`.