LIGHT ACTIVITIES

THE COLOUR OF OBJECTS

When light rays reach an object, this object absorbs some of the light and reflects some of it.
The reflected light enters our eyes.
An object always reflects its own colour.
White objects reflect all light.
This means they do not absorb any light.
Black objects absorb all light.
This means they do not reflect any light.

Colours. Picture from Stevopia

PRIMARY COLOURS OF LIGHT

The primary colours of light are red, green and blue.
When we mix the primary colours of light, we create new colours.
When we combine the three primary colours of light, we create white light.

The primary colours of light. Photo from Paul Nulty

DISPERSION OF LIGHT

Sir Isaac Newton discovered that white light (sunlight) is made up of many colours.
When the Sun shines and it rains at the same time, we see a rainbow.
This is because the raindrops act like tiny prisms: they separate the white light into the seven colours of the rainbow.
We say that prisms disperse white light into all colours.

Dispersion of light. Photo from universetoday.com

REFRACTION OF LIGHT

Light bends and changes direction when it passes from one transparent medium to another.
This is called refraction.
Water, clear glass, lenses and air refract light.
Lenses are transparent objects made of glass.
Lenses refract light.
They can be convex or concave.

Picture from BBC.com

REFLECTION OF LIGHT

When light hits an opaque object, it bounces off.
This is called reflection.
Reflected light allows us to see objects.
Most objects only reflect part of the light that hits their surface.
A mirror reflects all the light.

LIGHT AND OBJECTS

• Transparent objects. Light can pass easily through transparent objects.
• Translucent objects. Only some light can pass through translucent objects.
• Opaque objects. Light cannot pass through opaque objects.

LIGHT TRAVELS

Light travels in all directions at a speed of 300.000 kilometres per second.
We cannot see light moving.
Light travels in a straight line.
This is why we see shadows.