🔦 Light Sets Off on a Journey: How Is a Shadow Made?

Hello! Today we are going to follow the journey of light. How does light travel? How do shadows appear on a screen? Come on, let’s build a shadow theatre together!

Things that make their own light are called light sources. The Sun, a light bulb and a candle are light sources. The Moon doesn’t make light. It reflects light that comes from the Sun. So the Moon is not a light source.

Light spreads out from its source in every direction, and it travels in straight lines. If the holes in the cards are in line, light gets through. If one hole is moved, the light stops. About a thousand years ago, the scientist Ibn al-Haytham showed this with an experiment in a dark room.

Materials let light through in different ways. Transparent materials let almost all the light through, like clear glass. Translucent materials let some light through, like frosted glass. Opaque materials let no light through at all, like cardboard.

When we walk in the sunshine, our shadow follows us. When light hits an opaque object, it can’t get past it. That is why a shadow forms on the opposite side of the object from the light source. A shadow is a place the light can’t reach.

Let’s look at a ray diagram. Rays from the lamp pass the edges of the card and reach the screen. The card is opaque, so it blocks the light. Behind the card there is a dark area that light can never reach. This is a shadow.

Now let’s walk the card towards the lamp. The closer the card gets to the lamp, the bigger its shadow on the screen grows. The further away it moves, the more the shadow shrinks. Light travels in straight lines, so the size of the shadow depends on how far the object is from the lamp.

Now it’s shadow theatre time! We cut out a paper figure and fix it to a stick. We hold the figure between the torch and the screen. When the figure moves closer to the torch, its shadow grows, and when it moves away, the shadow shrinks. Tell your story with shadows!

Summary: light travels in straight lines. An opaque object blocks light, and a shadow forms behind it. The shadow is on the opposite side from the light source. When the object moves closer to the source, the shadow grows. Now try it in Shadow Theatre!