Question

The distance of an illuminated object from its light source is doubled while the luminous flux remains constant. Which is true of the illuminance on the object?1) The illuminance will be halved.2) The illuminance will quadruple.3) The illuminance will be multiplied by the square root of 2.4) The illuminance will be quartered.

Answer 1

4) is the answer ! hope this helps

Answer 2

4) The illuminance will be quartered.

Step-by-step explanation

According to the inverse square law of light, the illuminance of a light source is inversely proportional to the square of the distance from the source.

Mathematically:

`E\propto(1)/(r^2)`

where E = illuminance; r = distance from the light source

If the distance is doubled, then we have that:

`\begin{gathered} E\propto(1)/((2r)^2) \\ E\propto(1)/(4)((1)/(r^2)) \end{gathered}`

As we can see, the illuminance on the object will be quartered if the distance from the light source is doubled.