What percentage of light is reflected from a piece of glass?

Think it through first, then pick an option.

a 4 to 5 percent
b 40 to 50 percent
c 80 to 90 percent
d 95 to 96 percent

Answer and explanation

Correct answer: a 4 to 5 percent

An ordinary piece of glass reflects little, only 4% to 5%; the rest is refracted through. Near 80° or 90° of incidence the reflection does rise sharply.

Why the other options are wrong

b 40 to 50 percent: This is not the answer: An ordinary piece of glass reflects only 4% to 5%. This share is far larger; reflection climbs that high only when the angle of incidence is near 80° or 90°.
c 80 to 90 percent: This is not the answer: An ordinary piece of glass reflects only 4% to 5%. This share is far larger; reflection climbs that high only when the angle of incidence is near 80° or 90°.
d 95 to 96 percent: This is not the answer: 95% to 96% is the share that goes through the glass. The reflected share is only 4% to 5%.