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.
Pronounce these words:•Sound•Wave•Sources•Natural•Artificial•Transparent•Translucent•Opaque•Shadow•Penumbra•Speed
•Vacuum•Absorb•Reflect•Refract•Bounce•Mirror•Lens•Sound•Intensity•Pitch•Tone