ANSWER
4) The illuminance will be quartered.
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:
[tex]E\propto\frac{1}{r^2}[/tex]where E = illuminance; r = distance from the light source
If the distance is doubled, then we have that:
[tex]\begin{gathered} E\propto\frac{1}{(2r)^2} \\ E\propto\frac{1}{4}(\frac{1}{r^2}) \end{gathered}[/tex]As we can see, the illuminance on the object will be quartered if the distance from the light source is doubled.
