Question

If an illuminated spherical object has illuminance of 100 lx, the illuminance of a spherical object with twice the radius will be 400 lx. Is this true or false

Answer 1

False

Step-by-step explanation:

The illuminance is equal to the total flux divided by the surface area. If the spherical object has twice the radius, the surface area will be:

`\begin{gathered} A_{\text{ initial}}=4\pi r^2 \\ A_{\text{ final}}=4\pi(2r)^2=4\cdot4\pi r^2=4A_{\text{ initial}} \end{gathered}`

So, if the luminous flux is the same, and the surface area is increased, the illuminance will decrease.

Since 400 lx is greater than 100 lx, the statement is false.