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Lesson: Chapter 5 — Optics

5.4.2. Concave lenses 2 of 2

Images in a concave lens

A concave lens never forms a real image. Look through it and objects look smaller.

Activity 5.7

You will need: a concave lens, a white screen, a candle

  • Place a bright object, such as a lit candle, in front of a concave lens.
  • Put a screen on the other side and move the lens to see whether an image can be caught on it.

The observation

No image can be caught on the screen. Looking through the lens at the candle, it looks small — a virtual image. However far from the lens the object is, only a small, upright, virtual image is ever seen.

An object in front of a concave lens; the ray parallel to the axis spreads as if from the near focus, the ray through O goes straight on; traced back, dashed, they meet between F and the lens at a small upright image.

After Figure 5.45.

Convex mirror

Small, upright, virtual image — always.

Concave lens

Small, upright, virtual image — always.

The two diverging optics behave alike.