Light and Sound In this unit: Properties of light Reflection Colors Refraction Properties of sound Hearing PPT adapted from: http://science.pppst.com/lightoptics.html

AIM – Properties of Light WRITE NOW: How does light travel? Laser

Light travels VERY FAST – around 300,000 kilometres per second. At this speed it can go around the world 8 times in one second.

Light travels much faster than 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.

We see things because they reflect light into our eyes: Homework

Luminous and non-luminous objects A luminous object is one that produces light. A non-luminous object is one that reflects light. Luminous objects Reflectors

Shadows Shadows are places where light is “blocked”: Rays of light

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

Reflection Reflection from a mirror: Mirror Normal Angle of incidence Incident ray Reflected ray Angle of incidence Angle of reflection Mirror

Angle of incidence = Angle of reflection 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 !!!

Clear vs. Diffuse Reflection Smooth, shiny surfaces have a clear reflection: Rough, dull surfaces have a diffuse reflection. Diffuse reflection is when light is scattered in different directions

Using mirrors Two examples: 2) A car headlight 1) A periscope

Colour White light is not a single colour; it is made up of a mixture of the seven colours of the rainbow. We can demonstrate this by splitting white light with a prism: This is how rainbows are formed: sunlight is “split up” by raindrops.

The colours of the rainbow: Red Orange Yellow Green Blue Indigo Violet

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 red and green makes yellow Adding all three makes white again

Only red light is reflected Seeing colour The colour an object appears depends on the colours of light it reflects. For example, a red book only reflects red light: Homework White light Only red light is reflected

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 A white hat would reflect all seven colours: White light

Using coloured light If we look at a coloured object in coloured light we see something different. For example, consider a football kit: Shirt looks red White light Shorts look blue

In different colours of light this kit would look different: Red light Shirt looks red Shorts look black Shirt looks black Blue light Shorts look blue

Some further examples: Object Colour of light Colour object seems to be Red socks Red Blue Black Green Blue teddy Green camel Magenta book Homework

Using filters Red Filter Filters can be used to “block” out different colours of light: Red Filter Magenta Filter

Investigating filters Colour of filter Colours that could be “seen” Red Green Blue Cyan Magenta Yellow

Red Blue Green White Yellow Cyan Magenta

AIM: What is refraction? WRITE NOW: Why did the pencil look ‘broken’ in the glass of water?

Words – speed up, water, air, bent 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

Refraction Lab

AIM: How is light refracted through different shaped lenses? WRITE NOW: What is the difference between divergent and convergent?

Convex Mirrors

Convex Mirrors -Always right-side up and smaller than the object. -The image appears ‘behind’ the mirror.

Concave Mirrors

Concave Mirrors Parallel light ways are reflected through the same point in front of the object. This is called the focal point.

Concave Mirrors If the object is IN FRONT of the focal point, it appears right-side up and larger. If the object is BEHIND the focal point, it appears upside down and larger or smaller, depending on the angle of reflection.

Lenses A transparent material that either has one flat side and one curved side, or has two curved sides.

Concave (Diverging) Lens Use the ray box and the concave lens to investigate the behavior of light as it passes through the lens.

Concave (Diverging) Lenses Rays are bent outwards towards the ends of the lens.

Convex (Converging) Lenses Use the ray box and the concave lens to investigate the behavior of light as it passes through the lens.

Convex (Converging) Lenses Light rays bend towards the middle of the lens. The point at which these rays meet is the focal point.

Normal Vision

Far-Sighted Vision

Far-Sighted Vision

Near-Sighted Vision

Near-Sighted Vision

Words – slowly, low, high, quickly Sound – The basics We hear things when they vibrate. If something vibrates with a high frequency (vibrates very ______) we say it has a _____ pitch. If something vibrates with a low frequency (vibrates ______) we say it has a ____ pitch. The lowest frequency I could hear was… Words – slowly, low, high, quickly

Drawing sounds… This sound wave has a _____ frequency:

Drawing sounds… This sound wave has a _____ amplitude (loud): This sound wave has a _____ amplitude (quiet):

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

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

The Ear Label your diagram with the following: These bones are vibrated by the eardrum This 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

The Ear