Shadows

In Activity 11.3, an opaque object made a dark patch on the screen. Why?

Light travels in a straight line and cannot curve round the object. So an opaque object blocks the light, and the dark area where light cannot reach is its shadow.

Do translucent and transparent things make shadows too? Opaque objects make the darkest shadows. Translucent ones make lighter shadows. Even some transparent objects make faint shadows.

Activity 11.4 plays with shadows using opaque objects of different shapes and sizes. Try:

• removing the screen; removing the object; switching off the torch;
• changing the object's colour;
• moving the object closer to the screen, then closer to the torch;
• tilting it.

Each time, look at the shadow's shape and size.

What you find:

• You need three things for a shadow: a light source, an opaque object and a screen. Every day, the wall, floor or ground is the screen.
• The shape, size and sharpness of a shadow depend on where the object is compared with the light and the screen. Sometimes a shadow shows clearly what the object is; sometimes you cannot guess at all.
• A surprise: changing the colour of the object does not change the colour of its shadow. A red ball and a blue ball both make a dark shadow.

Shadow play, or shadow puppetry, has been part of our heritage for centuries: flat cut-out figures are held between a light and a screen. Regional styles include Charma Bahuli Natya (Maharashtra), Keelu Bomme and Tholu Bommalata (Andhra Pradesh), Togalu Gombeyaata (Karnataka), Ravana Chhaya (Odisha), Tholpavakoothu (Kerala) and Bommalattam (Tamil Nadu).