Always small, always upright

The idea

An object seen through a concave lens always appears erect and diminished, its size changing as its distance from the lens increases.

A different lens

Now look through a concave lens, thicker at the edges, at an object behind it. The object moves farther away.

Will the object ever look upside down?

• No. It always looks erect
• Yes, once it is far enough
• Yes, when it is very close

Look through the lens

Your eye looks through the concave lens. Move the object behind it from very close to very far.

Always erect and diminished

An object seen through a concave lens always appears erect and diminished. Its size changes as its distance from the lens increases.

This is just like a convex mirror: always erect, always smaller.

• Object behind the lens | How it looks
• Close | Erect, diminished
• Far away | Erect, diminished, and smaller

Notes

An object seen through a concave lens always appears erect and diminished; its size changes as its distance from the lens increases.

Check yourself

How does an object look through a concave lens?

Which lens can make an object look inverted?

Through a lens, an object looks smaller and erect at every distance. Which lens is it?

• Erect and enlarged when it is close. That is a convex lens. A concave lens always makes it look smaller.
• Always erect and diminished — correct. Yes. Near or far, it looks upright and smaller.
• Inverted when it is far. That is a convex lens. Through a concave lens, it always looks erect.
• Neither lens. A convex lens does, once the object is a little farther away.
• A concave lens, when the object is far. Through a concave lens, an object always looks erect.
• A convex lens, when the object is farther away — correct. Yes. A concave lens always shows it erect.
• A convex lens. A convex lens makes close things look bigger, and far things inverted.
• A concave lens — correct. Yes. It always shows things erect and diminished.
• A flat glass plate. Flat glass does not change the size at all.