Light presentation

• 1.

2. Light and Sound

• In this unit:

• Properties of light

• Reflection

• Colours

• Refraction

• Properties of sound

• Hearing

3. Part 1 Properties of Light

• Light travels instraightlines:

Laser 4.

• Light travels VERY FAST around 300,000 kilometres per second.

At this speed it can go around the world 8 times in one second. 5.

• Light travelsmuch fasterthan sound. For example:

• Thunder and lightning start at the same time, but we will see the lightning first.

2)When a starting pistol is fired we see the smoke first and then hear the bang. 6.

• We see things because theyreflectlight into our eyes:

Homework 7.

• Luminous and non-luminous objects

Aluminousobject is one that produces light. Anon-luminousobject is one that reflects light. Luminous objects Reflectors 8.

• Shadows

Shadows are places where light is blocked: Rays of light 9. Properties of Light summary

• Light travels in straight lines

• Light travels much faster than sound

• We see things because they reflect light into our eyes

• Shadows are formed when light is blocked by an object

10. Part 2 - Reflection

• Reflection from a mirror:

Incident ray Normal Reflected ray Angle of incidence Angle of reflection Mirror 11.

• The Law of Reflection

Angle of incidence = Angle of reflection In other words, light gets reflected from a surface at ____ _____ angle it hits it. The same !!! 12. Clear vs. Diffuse Reflection

• Smooth, shiny surfaces have aclearreflection:

Rough, dull surfaces have adiffusereflection. Diffuse reflectionis when light is scattered in different directions 13. Using mirrors

• Two examples:

1) A periscope 2) A car headlight 14. Colour

• White light is not a single colour; it is made up of a mixture of the seven colours of ther a i n b o w .

We can demonstrate this by splitting white light with a prism: This is how rainbows are formed: sunlight is split up by raindrops. 15. The colours of the rainbow:

• Red

• Orange

• Yellow

• Green

• Blue

• Indigo

• Violet

16. Adding colours

• White light can be split up to make separate colours.These colours can be added together again.

• The primary colours of light are red, blue and green:

Adding blue and red makes magenta (purple) Adding blue and green makes cyan (light blue) Adding all three makes white again Adding red and green makes yellow 17. Seeing colour

• The colour an object appears depends on the colours of light it reflects.

For example, a red book only reflects red light: White light Only red light is reflected Homework 18. A white hat would reflect all seven colours: A pair of purple trousers would reflect purple light(and red and blue, as purple is made up of red and blue): Purple light White light 19. Using coloured light

• If we look at a coloured object in coloured light we see something different.For example, consider a football kit:

White light Shorts look blue Shirt looks red 20.

• In different colours of light this kit would look different:

Red light Shirt looks red Shorts look black Blue light Shirt looks black Shorts look blue 21. Some further examples: Red Blue Red Blue Black Red Blue Red Red Black Blue Green Magenta book Green Green camel Green Blue teddy Black Green Red socks Colour object seems to be Colour of light Object Homework 22. Using filters

• Filters can be used to block out different colours of light:

Red Filter Magenta Filter 23. Investigating filters Yellow Magenta Cyan Blue Green Red Colours that could be seen Colour of filter 24. Red Magenta White Yellow Blue Green Cyan 25. Refraction Refraction is when waves ____ __ or slow down due to travelling in a different _________.A medium is something that waves will travel through.When a pen is placed in water it looks like this: In this case the light rays are slowed down by the water and are _____, causing the pen to look odd.The two mediums in this example are ______ and _______. Words speed up, water, air, bent 26. 27. 28. Sound The basics We hear things when theyvibrate .If something vibrates with ahigh frequency(vibrates very ______) we say it has a_____pitch. If something vibrates with alow frequency(vibrates ______) we say it has a____pitch. The lowest frequency I could hear was Words slowly, low, high, quickly 29. Drawing sounds This sound wave has a_____ frequency : This sound wave has a___ _frequency : 30. Drawing sounds This sound wave has a_____ amplitude(loud): This sound wave has a_____ amplitude(quiet): 31. Hearing problems

• Our hearing range can be damaged by several things:

• Too much ear wax!

• Damage to the auditory nerve

• Illness or infections

• Old age (not like Mr Richards)

32. Other sound effects

• Like light, sound can be

• Reflected sound reflections are called ______.

• Refracted this is why you might sound strange if you try talking underwater

33. The Ear Label your diagram with the following: These bones are vibrated by the eardrumThis tube carries the sound towards the eardrum This part is used to help us keep our balance This part picks up the vibrations This part of the ear contains many small hairs with turn vibrations into an electrical signal This part connects the ear to the mouth This part channels the sound towards the ear drum 34. The Ear