Question

A light bulb's brightness is reduced when placed behind a screen. The amount of visible light produced by the light bulb decreases by 25% with each additional layer that is added to the screen. With no screen, the light bulb produces 750 lumens. The lumen is a unit for measuring the total quantity of visible light emitted by a source. Select the correct equation that can be used to represent the lumens, L, after x screen layers are added.

Answer 1

It is an exponential function, since 25% of the light is lost by adding each screen, or remaining light is 1-0.25=0.75 of the previous brightness.

Thus, after x screens,
L(x)=L*0.75*0.75... *0.75  (x times)
=L*0.75^x

Answer 2

Answer:

B.  L = 750(0.75)x