Moving the object

The idea

The shape, size and sharpness of a shadow depend on the position of the object relative to the light source and the screen.

Big shadow, small shadow

A card is held between a lamp and a wall. Its shadow does not always look the same.

If you move the card nearer to the lamp, what happens to its shadow?

• It becomes bigger
• It becomes smaller
• It stays the same size

Move and turn the card

Slide the card nearer to the lamp and nearer to the wall. Then turn the card. The picture is a model.

Position matters

Nearer to the lamp the shadow was bigger and less sharp. Nearer to the screen it was smaller and sharper. Turning the card changed the shape.

The shape, size and sharpness of a shadow depend on the position of the object relative to the light source and the screen.

• What we did | The shadow
• Card nearer to the lamp | Bigger, less sharp
• Card nearer to the screen | Smaller, sharper
• Card turned | Different shape

Notes

The shape, size and sharpness of a shadow depend on the position of the object relative to the light source and the screen.

Check yourself

The card is moved nearer to the lamp. The shadow becomes …

The card is moved close to the screen. The shadow becomes …

Turning the card changes which feature of the shadow?

What can change a shadow’s shape, size and sharpness?

• smaller. A card nearer to the lamp makes a bigger shadow.
• bigger — correct. Yes! The shadow grows.
• exactly the same. The position of the card changes the shadow.
• much bigger but just as sharp. A card close to the screen gives a smaller shadow.
• bigger and less sharp. That happens when the card is nearer to the lamp.
• smaller and sharper — correct. Yes! Close to the screen the shadow is small and sharp.
• Its shape — correct. Yes! A turned card gives a narrower shadow.
• Its colour. The colour of a shadow does not depend on how the card is turned.
• Whether the lamp is a source of light. The lamp stays a source of light. Only the shadow changes.
• Nothing, a shadow is always the same. The shadow changes with the position of the object.
• The position of the object, the lamp and the screen — correct. Yes! Their positions matter.
• Only the colour of the object. Changing the colour of an opaque object does not change its shadow.