2. Light and sound. What do they have in common?

3. Light waves Sound waves Light and sound travel in waves.

4. Light is a form of electromagnetic energy. Sources of light NaturalArtificial http://www.bbc.co.uk/schools/ks2bitesize/science/physical_processes/light_dark/play.shtml

5. Objects can be transparent, translucent or opaque

6. 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.

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

8. shadow penumbra http://www.bbc.co.uk/schools/ks2bitesize/scie nce/physical_processes/light_shadows/play.sh tml

9. What’s happening?

11. Reflection is the change in direction of a wave when it hits a surface and bounces off.

13. Different colour, different reflection

14. What’s happening?

15. Refraction is the change in direction of a wave when it passes from one medium to another.

16. Refraction is a useful property to make lenses

17. What do we use lenses for?

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

20. THE SPEED OF SOUND IN… Air340 m/s Water1500 m/s Iron5130 m/s

21. The reflection of sound waves produces the echo Distance (metres) 0 0.1 340 Time (seconds) 17 Speed: 340 m/s ECHO An echo is heard at more than 17 metres.

22. Fishing boats use sonar to detect shoals of fish. reflected sound emitted sound

23. 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.

24. 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