2. Sound D. Crowley, 2008

3. Sound To know how sound travels, and how this is affected by the medium it travels through

4. Coloured Filters A blue filter All colours apart from blue light are absorbed (blue passes through and can be seen) A red & blue filter All colours apart from red light are absorbed (red passes through but the blue filter absorbs all colours except blue, so the red is absorbed and no light passes through) A green & red filter All colours apart from green light are absorbed (green passes through but the red filter absorbs all colours except red, so the green is absorbed and no light passes through)

5. Sound What is sound How fast does is travel (faster than light)? How does it travel (can it travel in space)? Sound is a form of energy, produced whenever an object vibrates (a guitar string / vocal cords / loudspeaker etc…) Sound travels as a wave, similar to light, but for sound to travel it needs to vibrate particles Sound cannot travel through a vacuum (no particles to vibrate) - in space, no-one can hear you scream!

6. Sound Sound travels by vibrating one particle, which vibrates it neighbours, which vibrate theirs etc… Vibration in same direction as wave is traveling Wave traveling

7. Sound Sound travels at different speeds through different substances, traveling at 330 m/sec through air (light travels at 300’000 km/sec or 300’000’000 m/sec)! Why does sound travel so much slower than light? How do you know this to be true? Watch a firework display / thunder and lighting during a storm, and you always see the light before you hear the noise Sound travels as a wave, but it needs to vibrate particles to travel

8. Thrust SSC

9. Listen Up What do you think will happen to the speed of sound through different objects? Remember, sound is caused by the wave bumping into particles, which bump into their neighbours, which bump into theirs… Think of the particle model for a solid, liquid, gas and then a vacum – which will sound travel fastest through?

10. Sound & Matter Sound needs a substance to travel through and travels by particles vibrating - which state of matter does sound travel fastest through? GasSolidLiquid Sound waves travel fastest through solids - the particles in a solid are closer together than in a gas or a liquid meaning vibrations are more easily passed from particle to particle and so sound travels faster

11. Vacuum What about a vacuum? Vacuum There is air inside the bell jar so the sound can travel and be heard Vacuum pump on Remove the air from the bell jar and the sound cannot be heard because there are no air particles to vibrate

12. Bell Jar

13. Scream Explain the tag line from Alien “in space no one can hear you scream” Remember, unlike light, sound can only travel by vibrating particles In space there are no particles, so a sound wave will not travel (meaning it is silent in space)

14. What Sound Complete the what makes the sound worksheet