Chapter 16, Problem 34A

To determine

The factors on which illumination isdirectly proportional and inversely proportional to.

Answer to Problem 34A

The illuminance of the light source is directly proportional to luminous flux and inversely proportional to the square of the distance between light source and screen.

Explanation of Solution

Introduction:

Illumination is an observable property and a property of light, known as the brightness of light.Illuminance measures the luminous flux per unit of area.

The illuminance of the light source is equal to the ratio of the luminous flux of the light source to the surface area. Therefore, the illuminance of the light source is directly proportional to luminous flux.

Again, the surface area is directly proportional to the radius, which is the distance of the screen from the light source. i.e. illuminance is inversely proportional to the square of the distance between light source and the screen.