Boxi Learn › Physics › Stage 3 · Structure and Evidence
Where does a lens put the picture?
Covering half the lens cuts off half the picture.
Rays from one point of the object meet again at one point of the image; move the object closer (but still beyond f) and the image moves away and grows; inside f there is only an upright, magnified virtual image, as in a magnifier.
A friend says that if a fly lands on a camera lens, the photo will have a black hole where the fly is. Using the words “every point”, “rays” and “brightness”, explain what really happens.
Hold a magnifying glass between a bright window and a white wall or sheet of paper. Move the paper until the window appears sharp — upside down. Then cover half the glass with your hand and watch. Never look at the Sun through a lens or focus sunlight on anything.