Video Transcript
Which of the following materials
could a convex lens be made out of? (A) Wood, (B) copper, (C) steel,
(D) glass, (E) concrete.
Remember that a lens is a piece of
transparent material with a particular shape that can be used to change the
direction that light rays are traveling in. A transparent material allows light
to pass through it. In other words, it is
see-through. So, a lens must be made from a
material that light can pass through.
So, now let’s think about each of
the five materials that we’ve been given as possible answers. We know that wood is not
transparent. We wouldn’t expect to be able to
see through a tree, for example. Light cannot pass through wood, so
wood is not a suitable material for a lens. So (A) cannot be the correct
answer.
Similarly, metals like copper or
steel aren’t transparent. We wouldn’t expect to be able to
see through a copper coin or a steel saucepan. So, (B) and (C) cannot be the
correct answer.
Glass, however, is transparent. We know that light can pass through
things like glass windows, which are used to let sunlight into buildings. So, option (D) could be the correct
answer.
Finally, concrete is not
transparent. Concrete is often used to build
walls and pavements, which are not see-through. So, (E) cannot be the correct
answer.
So, the only material in this list
that lets light pass through it is glass. This means that glass is the only
one of these materials that a lens could be made out of. In fact, it is very common for
lenses to be made from glass. The lenses in magnifying glasses or
in eyeglasses for correcting vision are often made from glass. So, option (D), glass, is the
correct answer.
