A part of a hollow sphere

The idea

Mirrors whose reflecting surfaces are spherical, shaped like a part of a hollow sphere, are called spherical mirrors; they are a common type of curved mirror.

Meena's strange mirrors

At a science centre, Meena looks into a row of curved mirrors. In one, her face looks very large. In another, she looks tiny. The guide says: "These are not plane mirrors. These are spherical mirrors."

What do you think the surface of a spherical mirror is shaped like?

• A part of a hollow ball
• Flat, like a window pane
• Any wavy shape at all

Does it fit the sphere?

Here is an imaginary hollow sphere, seen from the side. Lay each mirror on it. Which mirror follows the sphere all along?

A part of a hollow sphere

Mirrors whose reflecting surfaces are spherical, shaped like a part of a hollow sphere, are called spherical mirrors. They are a common type of curved mirror.

A shiny metal spoon is curved too. It acts like a mirror, and you can see your image in it.

• Mirror | Is it a part of a sphere?
• Flat mirror | No. It is a plane mirror
• Curved mirror A | Yes. It is a spherical mirror
• Curved mirror B | No. It is curved, but not spherical

Notes

Mirrors whose reflecting surfaces are spherical, shaped like a part of a hollow sphere, are spherical mirrors: a common type of curved mirror.

Check yourself

What is the surface of a spherical mirror shaped like?

Spherical mirrors are a common type of…

A mirror is curved, but its surface does not follow any sphere. Is it a spherical mirror?

Which of these acts like a curved mirror?

• A whole glass ball. It is only a part of a hollow sphere, not a whole ball.
• A flat sheet. A flat mirror is a plane mirror, not a spherical mirror.
• A part of a hollow sphere — correct. Yes. That is why it is called spherical.
• plane mirror. A plane mirror is flat. A spherical mirror is curved.
• curved mirror — correct. Yes. Their surface is curved like a part of a sphere.
• window glass. Window glass lets light pass through. A mirror sends light back.
• Yes, as long as it is shiny. Being shiny makes it a mirror. Its shape decides whether it is spherical.
• Yes. Every curved mirror is spherical. Spherical mirrors are one common type of curved mirror. A curved mirror can have another shape.
• No. It is a curved mirror, but not a spherical one — correct. Yes. Only a mirror whose surface is a part of a sphere is spherical.
• A shiny metal spoon — correct. Yes. You can see your image in its curved surface.
• A flat window pane. It is flat, and light passes through it.
• A sheet of paper. Paper does not form an image of your face.