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FIND OUT MORE. Atoms 157 • Colour 180 • Eye 140 • Lenses 181 • Matter 156

WHY IS A SWIMMING POOL DEEPER THAN IT LOOKS?

Refraction can make things look closer than they really

are. The difference in speed between light travelling

through water and through air means that, from the

surface, a 4 m (13 ft) pool appears to be just 3 m (10 ft)

deep. Glass is another material that refracts light. It is

used to make spectacles and other lenses.

WHAT HAPPENS WHEN YOU LOOK IN A MIRROR?

At first sight your image is identical to you. But

a closer look shows that as you lift your right hand

your image raises its left. Reflection always flips an

image from left to right. If you hold up a sheet of

paper with writing on it, the image in the mirror

shows the writing back to front.

WHY IS LASER LIGHT SO SPECIAL?

Laser light does not spread out in the way that light

from other sources does. All the light waves in laser

light are precisely in step with each other. As a result,

laser light can be concentrated and controlled far

more accurately. It can carry television and other

signals over great distances without losing quality.

A laser produces an incredibly powerful,

concentrated form of light. Inside a laser,

light waves are bounced back and forth

between two mirrors to build up energy

before being released as a narrow beam.

Light travels more slowly through some

materials than others. The change in speed

can cause light rays to change direction.

This directional change is called refraction.

Light rays reflect (bounce) off objects. The

Moon shines because it reflects light from

the Sun. Smooth surfaces, such as mirrors,

reflect light in one direction.

4 SEEING THINGS

Refraction makes this girl’s body look closer

when it is seen through the surface of

the water. This is because the light rays

change direction as they travel from

water into air.

1 REFRACTION

A laser beam is refracted

(changes direction) when it

passes from air into a block

of transparent plastic.

MIRROR MIRROR 3

If you stand between two

mirrors that are directly opposite

each other, you will see

reflections of your reflection

vanishing off into the distance.

REFRACTION

REFLECTION

LASER EYE SURGERY 3

Extremely fine laser

beams are used to perform

operations on the human eye.

LAW OF REFLECTION 3

The law of reflection says

that the angle of the beam

bouncing off a mirror will be

equal to the angle at which

it arrived.

LASER

The beam hits the mirror,

and is reflected just like a

billiard ball bouncing off

the side of a table

The laser beam

leaves the block. It has

moved sideways, but is still

parallel to the original beam

A glass mirror

is coated on one side with a

thin, reflective layer of metal

Fine laser

beams

can be very

precisely

controlled

Multiple reflections

alternately flip from

left to right

Refracted laser

beam inside

plastic block

The laser beam

travels in a straight

line through the air

Laser beam

in air

Boy

looking in

mirror