Video Transcript
Which of the following is a convex
lens? (A), (B), (C), (D), or (E)?
Let’s first remind ourselves of
what a convex lens looks like. When viewed from the side, a convex
lens should have the same shape as the area of overlap between two circles. This means that a convex lens
always has two curved surfaces and is thickest in the middle and thinnest at the
edges. Note that it is perfectly fine to
rotate a convex lens. It doesn’t matter whether the lens
is upright or on its side or somewhere in between. As long as it has this shape, it is
still a convex lens.
Now, let’s look at the options we
have been given. We can rule out shapes (A), (D),
and (E) straightaway. This is because all of these shapes
only have straight sides. A convex lens must have two curved
surfaces. So, none of these can be the
correct answer.
Next, let’s look at option (B). Option (B) does have two curved
surfaces. However, this shape is thicker at
the edges than it is in the middle. So this shape is not a convex
lens. Option (B) is incorrect.
Finally, let’s look at option
(C). Option (C) has two curved
surfaces. And it is thicker in the middle
than it is at the edges. This matches our description of a
convex lens.
To double-check our answer, we can
recall that when viewed from the side, a convex lens looks like the overlap between
two circles. Is this true for option (C)? Well, yes. Option (C) is the same shape as the
overlap between two circles, placed vertically like this. So option (C) correctly shows a
convex lens. Option (C) is the correct
answer.
