Caves in or bulges out
Which way the shiny surface curves gives the mirror its name.
Two mirrors in one spoon
A shiny metal spoon acts like a mirror on both sides. The inner side is hollow. The outer side bulges.
Do you think both sides of the spoon are the same kind of mirror?
What this lesson covers
The idea
A spherical mirror whose reflecting surface curves inwards is a concave mirror; one whose reflecting surface curves outwards is a convex mirror.
Two mirrors in one spoon
A shiny metal spoon acts like a mirror on both sides. The inner side is hollow. The outer side bulges.
Do you think both sides of the spoon are the same kind of mirror?
- No, the two sides are different kinds of mirror
- Yes, a spoon is one mirror
- No, only one side is a mirror
Look into a spoon
Look at the inner side, then the outer side. Watch your face, and see how the shiny surface curves.
Concave and convex
A spherical mirror whose reflecting surface curves inwards is a concave mirror. One whose reflecting surface curves outwards is a convex mirror.
A way to remember: a concave mirror caves in. In drawings, the non-reflecting side of a mirror is shown shaded.
- Side of the spoon | Kind of mirror
- Inner side: curves inwards | Concave mirror
- Outer side: bulges outwards | Convex mirror
Notes
A spherical mirror whose reflecting surface curves inwards is a concave mirror; one whose reflecting surface curves outwards is a convex mirror.
Check yourself
The eye looks at the shiny surface of this mirror. The shaded side does not reflect. What kind of mirror is it?
The reflecting surface of a mirror bulges outwards, towards you. What is it?
Meena looks into the inner, hollow side of a shiny spoon. It works like a…
In a drawing of a spherical mirror, what does the shaded side show?
- A plane mirror. A plane mirror is flat. This one is curved.
- A convex mirror. A convex mirror bulges out towards the eye. This one curves inwards.
- A concave mirror — correct. Yes. The shiny surface curves inwards, away from the eye in the middle.
- A plane mirror. A plane mirror is flat. It does not bulge.
- A concave mirror. A concave mirror curves inwards, like a cave.
- A convex mirror — correct. Yes. A reflecting surface that curves outwards makes a convex mirror.
- concave mirror — correct. Yes. The inner side curves inwards.
- convex mirror. The outer side of the spoon is the convex mirror. The inner side curves inwards.
- plane mirror. A spoon is curved, not flat.
- The non-reflecting side — correct. Yes. The shiny reflecting surface is the side that is not shaded.
- The reflecting side. The reflecting side is left unshaded. The shading marks the back.
- The side light passes through. Light does not pass through a mirror. It is reflected.