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Sound and Light Study Sheet

- sound and light are forms of energy- sound and light can be powerful enough to hurt you

- both sound and light energy travel in waves

- light travels through the air almost a million times faster than sound (thats whyyou see a lightning flash before you hear thunder)

Sound

- all sounds are created through vibrations- when an object vibrates, it causes air molecules to bunch and move outward as

sound waves- sounds can also travel through solids and liquids (metal, water)

- sounds travel faster through solids than it does through the air (20 times faster

through steel)

- sound travels much farther under water

How we hear

- outer part of ear acts like a satellite dish, collecting sound waves and channelingthem inside your ears. The sounds reach the eardrums and make them vibrate.

- In the middle ear, there are 3 bones the hammer, anvil and stirrup. These are the

smallest bones in your body. They transfer vibrations from the eardrum to thecochlea. The cochlea sends signals to the brain. The brain processes what type of

sound you heard.

- You hear your own voice through vibrations that travel through the bones in your

skull to your inner ear.

Pitch and Loudness- waves have high points called crests, and low points called troughs.- A wavelength is the distance from one wave crest to another.

- Sound is measured in cycles per second orhertz- Long wavelengths have low frequency and short wavelengths have high

frequency.

- Sounds can be either high or low (pitch)

- High pitch has a high frequency (short waves), low pitch low frenquency (longwaves)

The study of sounds and how it travels is called acoustics. When sound waves strike

objects, they may be either reflected or absorbed.

Not all surfaces reflect sound soft surfaces absorb sounds (no echo)

Musical sounds are called tones. They are made by vibrations. The difference between a

musical tone and a noise is that the vibrations in a tone are regular (controlled).

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Types of instruments: String(guitar, violin, piano),Percussion (drums, xylophone) and

Wind(trumpets, recorders)

Light

- light waves always travel along straight paths.

- Shadows are formed when light rays are blocked by a solid object (tree, person)- The size of the shadow depends on how close the object blocking the light is to

the source of light.

- Light is the fastest thing in the universe (it travels 300,000 km a second)

How we see

- we can see the world around us because light is reflected from the objects we are

looking at.- The dark area of the eye is called the pupil. It becomes bigger in dim light to let as

much light as possible.

- Light enters the eye through a clear lens that sits just behind the pupil. The lens

allows you to focus at different distances.- The lens directs the light onto the retina sends signals to the brain.

- Each eye sends a slightly different image to the brain. The fields of visionoverlap, helping us judge distance and depth.

Colour

- the white light from the sun is actually a combination of different colours called

the spectrum (a rainbow shows all visible colours of the spectrum)

- Primary colours (red, green, blue), other colours can be made by mixing the

primary colours (red-green yellow, red-blue purple, blue-green cyan)

Reflection- all objects reflect light.- A smooth surface forms a reflection because it reflects the light that strikes it

evenly. The shinier the surface, the clearer the image will be.

- A curved, reflective surface around a car headlight is used to focus light in a tightbeam.

Light does not always travel at the same speed. When light passes from onetransparent material to another, (from air to glass) they change speed.

Refraction: bending of light as it travels from one transparent material to another

Convex lens: lens that curves outwards from the centre. It makes objects seen through it

look bigger. Helps farsighted people. Ex. Magnifying glass

Concave lens: lens that curves inwards. Bends light outwards, making objects looksmaller. Helps nearsighted people.

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