Light and sound.What do they

have in common?

Light waves

Sound waves

Light and sound travel in waves.

Light is a form of electromagnetic energy.Sources of light

Natural Artificial

http://www.bbc.co.uk/schools/ks2bitesize/science/physical_processes/light_dark/play.shtml

Objects can be transparent, translucent or opaque

• They absorb some light, and they allow some to travel through.

• They do not allow light to travel through.

• They allow light to travel through.

Light travels at a speed of about 300,000 km/s in a vacuum and in air.

shadow

penumbra

http://www.bbc.co.uk/schools/ks2bitesize/science/physical_processes/light_shadows/play.shtml

What’s happening?

Reflection is the change in direction of a wave when it hits a

surface and bounces off.

Different colour, different reflection

What’s happening?

Refraction is the change in direction of a wave when it passes

from one medium to another.

Refraction is a useful property to make lenses

What do we use lenses for?

Sound is a form of mechanical energy produced by the vibration of an

object.

THE SPEED OF SOUND IN…

Air 340 m/s

Water 1500 m/s

Iron 5130 m/s

The reflection of sound waves produces the echo

Distance (metres)

0 0.1

34 0

Time (seconds)

17

Speed: 340 m/s

ECHO

An echo is heard at more than 17 metres.

Fishing boats use sonar to detect shoals of fish.

reflected sound

emitted sound

The qualities of sound

Intensity depends on the amplitude of the sound waves.

Pitch depends on the frequency of the sound waves.

Tone allows you to identify the source of a sound which has the same frequency and intensity.

soft sound

loud sound

low pitched sound

high pitched sound

SEE INTENSITITES OF SOME SOUNDS.

CLICK ON THE SOUND ICON TO LISTEN TO THE SOUND.

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