A light bulb emitting 1750 Im of luminous flux shines on a book that is 3.0
m away. What is the illumination on the book?*

- 15 lx
- 101
- 25 IX
- 461x

The illumination on the book is 15 lx.

When the light emitted from a source, the power of that emitted light is measured by the Luminous Flux. Luminous Flux varies from the total power emitted by a light source.

When the light emitted from a source falls on the surface of the object placed at a certain distance, the surface illuminates the light flux. This property of illuminating the light from the surface of the object is called illumination.

Given that, a light bulb emitting the light having luminous flux of 1750 lm.

The emitted light falls on the surface of the book which is places at a distance of 3m.

The illumination can be calculated as given below.

Where E is the illumination of the light, P is the luminous flux and d is the distance of the object.

Hence, the illumination on the book is 15 lx.

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The illumination of the book is found to be approximately equal to 15 lx.

Option 1.

Explanation:

Luminous flux is the measure of power of the light emitted from a source and illumination is the property of the light to illuminate a given surface when it falls on the surface. So the measure of the region the light flux illuminates the surface is termed as illumination.

As here the luminous flux is given as 1759 lm and the distance of the object which has to be illuminated is placed 3 m away from the source ,the illumination is found to be directly proportional to the luminous flux and inversely proportional to the square of the distance between them

So, the illumination of the book is found to be approximately equal to 15 lx.

no. dot product   =0 when vecs at right angles