Big, then upside down

The idea

A concave mirror forms an erect, enlarged image of a nearby object; as the object moves farther away the image becomes inverted, first enlarged and then smaller and smaller.

Meena and her brother

In one curved mirror at the science centre, Meena's face, close to the mirror, looked very large. Her brother, standing a little farther away, looked upside down!

Could one concave mirror show both?

• Yes. It depends on how far away the object is
• No. They must have looked into two different mirrors
• No. A mirror always shows things the same way

Move the object away

Start very close to the concave mirror. Move the object farther, one step at a time. Watch the image you see in the mirror.

Erect when near, inverted when far

A concave mirror forms an erect, enlarged image of a nearby object. As the object moves farther away, the image becomes inverted, first enlarged and then smaller and smaller.

Erect means upright. Enlarged means bigger than the object. Diminished means smaller. Torch reflectors and the headlights of cars and scooters are concave. A dentist's mirror is concave: held close to the teeth, it gives an enlarged view.

• Object | Image in a concave mirror
• Close to the mirror | Erect, enlarged
• A little farther | Inverted, enlarged
• Farther | Inverted, same size
• Far away | Inverted, diminished (smaller and smaller)

Notes

A concave mirror: a nearby object gives an erect, enlarged image. Farther away, the image is inverted, first enlarged, then smaller and smaller.

Check yourself

A dentist holds a small concave mirror close to a tooth. How does the tooth look in it?

An object moves farther and farther from a concave mirror. Once the image turns upside down, what happens to its size?

Meena's brother stood a little farther from the concave mirror and looked upside down. What do we call such an image?

Which of these uses a concave mirror?

• Erect and enlarged — correct. Yes. A nearby object gives an erect, enlarged image.
• Inverted and diminished. That happens when the object is far from a concave mirror. The tooth is close.
• Erect and the same size. A plane mirror gives the same size. A concave mirror enlarges a nearby object.
• It stays the same size. Its size changes as the object moves. It gets smaller and smaller.
• It keeps getting bigger. It is enlarged just after it turns, but then it gets smaller and smaller.
• It is enlarged at first, then gets smaller and smaller — correct. Yes. That is what you saw when you moved the object away.
• Inverted — correct. Yes. An upside-down image is inverted.
• Erect. Erect means upright. His image was upside down.
• Diminished. Diminished is about size: smaller. Upside down is called inverted.
• The side-view mirror of a scooter. Side-view mirrors are convex. You will see why in the next lesson.
• The reflector of a torch — correct. Yes. Torch reflectors are concave.
• A wall mirror for combing your hair. A wall mirror is usually a plane mirror: same size, erect.