Light and Sound In this unit: Properties of light Reflection Colours Refraction Properties of sound Hearing

Part 1 – Properties of Light Light travels in straight lines: Laser

Light travels VERY FAST – around 300,000 kilometers 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

Energy in Light -There is a lot of energy in light. -For example, when you stand in the sun you feel the sun’s energy through heat. -If you absorb too much of that energy, you can get a sunburn. -A lamp doesn’t have as much energy as the sun- you can’t get sunburned by a lamp. -However, a lamp does give off heat because of the electric current it takes to make it work.

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. Light gives off energy in the form of heat.

Part 2: Reflection -When light hits an object, the object affects the path of the light. -An object can absorb light, make it bounce off, or let it pass through. -Some light energy is absorbed. Darker objects absorb more light energy-that’s why you are hotter when you wear dark colors on a hot day. -Objects don’t absorb all the light that hits them. Some of the light bounces off. Reflection is the bouncing of light from a surface.

Part 2:Reflection -Usually, light scatters in many directions when it is reflected. -A smooth surface reflects light in a clear and predictable pattern. -Have you ever seen a reflection in clear windows on a building? -Looking in a mirror can also get you a smooth reflection, but it gives you a backward image.

Reflection from a mirror: Normal 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 !!!

Refraction When light moves from water to air, its speed changes. The change in speed makes the beam of light bend. This bending of light is called refraction. Refraction is bending light. When a pen is placed in water it looks like this: Refracted light can make a solid object look like it is broken into two parts. It looks like that because the light from the part of the pencil that is under the water reaches your eyes on a different path.

Translucent Materials -Materials that let some light through are called translucent. An example of a translucent material is a frosted light bulb.

Transparent Materials -A transparent material allows most of the light that hits it to pass through it. -Most glass, water, and some plastics are transparent. -Transparent objects don’t scatter light, but they do refract it.

Opaque Materials -Materials that do not allow any light to pass through them are opaque. -Opaque materials absorb all the light into them. -Metal, wood, and most of your body is opaque.

Color White light is not a single color; it is made up of a mixture of the seven colors of the rainbow. We can demonstrate this by splitting white light with a prism:

Light and Color -As light enters a prism, the light waves change directions and separate (this is an example of refraction). -You are able to see all the colors of the rainbow when the colors separate. -You can remember all the colors of the rainbow with ROYGBIV. -When have you seen a rainbow of color?

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

Lenses -A lens is a curved, transparent object that refracts light. -There are different types of lenses with different types of curves.

Convex Lens -A convex lens is thicker in the middle than at the edges. -As light waves move through the lens, they bend towards the thickest part-the middle. -A convex lens makes light waves come together and make objects appear larger or magnified.

Concave Lens -A concave lens is thicker at the edges than in the middle. -As light waves enter the lens, they bend toward the thicker part- the ends. -The concave lens makes light waves spread out and this makes objects appear smaller.

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

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 (not like Mr Richards)

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