Light and Sound In this unit: 1)Properties of light 2)Reflection 3)Colors 4)Refraction 5)Properties of sound 6)Hearing
What is light? Light is a kind of energy. Without light energy you could not see anything!!!!!!!! Light energy gives things colors, helps plants to grow, can power solar batteries to make electricity and is used in lasers.
Part 1 – Properties of Light Light travels in straight lines: How does the following experiment prove this?????? Laser
Shadows Shadows are places where the straight lines of light are “blocked”: Rays of light
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: 1)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 blast 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 objectsReflectors
Properties of Light summary 1)Light travels in straight lines 2)Light travels much faster than sound 3)We only see things because they reflect light into our eyes 4)Shadows are formed when light is blocked by an object 5)Light is a form of energy like heat and electricity
Part 2 - Reflection Reflection from a mirror: What do you notice about where the mirror puts the light you shine into it? Incident ray Normal Reflected ray Angle of incidence Angle of reflection Mirror
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
Absorbing Light Stopping light is called absorption. When light hits most objects, some of the light bounces off and the rest is absorbed. Smooth shiny objects reflect most of the light. Dull objects absorb most of the light that hits them an reflects the rest. What you see when you look at it is the light that bounces off of it.
Absorption Opaque Objects-Reflects or absorbs all the light. You cannot see through opaque objects. Can you name some opaque objects? Translucent Objects-Reflects and absorbs some light. You can see a blurry or fuzzy image when you look through it. Can you name some opaque objects? Transparent- Does not reflect or absorb light. You see a clear image when you look through it. Can you name some transparent objects?
Using mirrors Mirrors reflect all the light! Two examples: 1) A periscope 2) A car headlight
Color White light is not a single color; 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. Prisms bend or refract light!
The colors 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: This is different than paint primary colors!!! 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
Seeing color The color an object appears depends on the colors of light it reflects. For example, a red book only reflects red light: White light Only red light is reflected
A white hat would reflect all seven colors: 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
Using colored light If we look at a colored object in colored light we see something different. For example, consider a football kit: White light Shorts look blue Shirt looks red
In different colors of light this kit would look different: Red light Shirt looks red Shorts look black Blue light Shirt looks black Shorts look blue
Some further examples: ObjectColour of light Colour object seems to be Red socks Red BlueBlack GreenBlack Blue teddy RedBlack Blue Green Green camel Red Blue Green Magenta book Red Blue Green
Using filters Filters can be used to “block” out different colours of light: Red Filter Magenta Filter
Refraction (http://www.brainpop.com/science/seeall/) (http://www.brainpop.com/science/seeall/) (http://www.brainpop.com/science/seeall/) 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, medium)
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: 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: 1)Too much ear wax! 2)Damage to the auditory nerve 3)Illness or infections 4)Old age (not like Mrs. Powers)
Other sound effects… Like light, sound can be… 1)Reflected – sound reflections are called ______. 2)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