KS3
Waves
Have you ever wondered how you hear things or why a rainbow appears in the sky when it rains?
In this topic you will learn what a wave is.Â
Types of waves
Waves aren't just the type you can surf on at the beach. There are many types of waves, like sound waves and light waves.
The topic of waves covers how we detect these waves and the way they move.
Speed of light
Light is incredibly fast. Light travels roughly a million times faster than sound.
If you had the power to move at the speed of light, you could circle the world 7.5 times in a minute!
That's why you will always see lightning before you hear thunder.
In space, light travels at 300 million meters per second.
Observed waves
There are waves we can see, and there are waves that go undetected by the human eye.
Waves in the sea undulate in a transverse motion.
Meaning they rise and fall smoothly and travel in a crosswise direction. Think of a ripple in a pond spreading outwards in all directions.
The electromagnetic spectrum including visible light.
Where sound waves cannot move through space, light waves can move through a vacuum. Light travels as waves in a straight line.
Light waves take 8 minutes to travel from the sun to earth. Think of all the things you can do in 8 minutes.
EM waves
What is a ray diagram and how does it show light transmission?
Ray Model
Use of ray model to explain imaging in mirrors, the pinhole camera, the refraction of light and the action of a convex lens in focusing (qualitative); the human eye.
Photo-sensitive
Light transferring energy from source to absorber leads to chemical and electrical effects; photo-sensitive material in the retina and in cameras.Â
Frequencies
Colours and the different frequencies of light, white light and prisms (qualitative only); differential colour effects in absorption and diffuse reflection.
Reflecting
When a wave meets a barrier, it will reflect off the surface.
Sea defences like harbour walls are so effective at protecting infrastructures inland because they reflect the waves away.
If you drop something into a bath you will see the waves reflect off the sides and change direction.
Light
The transmission of light through materials: absorption, diffuse scattering and specular reflection at a surface
The similarities and differences between light and in matter.
Superposition
Two things can happen when waves meet, depending on how they meet. If they meet out of sync they can cancel each other. When they meet in sync they add together, creating a higher wave.
Superposition
There are two ways to show superposition.
One way is by using a laser. The light from the laser pass through two slits in the barrier.
These two slits act like the light source, so two separate sets of light rays will spread out simultaneously. The resulting image will be a pattern of light and dark bands on the screen.
The second way is to use a ripple tank to watch the waves reflect and superposition occur.
How is a camera similar to an human eye?
Sound waves
Sound waves are produced by anything or substances that vibrate. The only place that sound is unable to travel through is space. Sound can travel through solids, liquids and gases.
Sound waves move through solids and liquids much faster than air. Through air sound waves travel at 343 m/s.Â
Soundwaves are longitudinal waves
Sound waves travel in the same direction as the vibrations are moving. Longitude is measured from east to west so it means running lengthwise.
Humans range of hearing
Most humans are able to hear a range between 20Hz and 20,000 Hz. Low pitch is 20Hz. High pitch is 20,000 Hz. Compairing this to animals, dogs are able to reach 60,000 Hz depending on their age and breed, which is much greater than humans. Pigeons are able to hear sounds as low as 0.05 Hz.
Ways to detect and use sound
If I were to pop a balloon next to you, the sound would create vibrations in the air.
Vibrations from the balloon pop, funnel down the ear canal and hit our eardrum.
The eardrum vibrates, causing the three bones (ossicles) behind it to vibrate too.
The ossicles connect to the cochlea.
The cochlea uses the auditory nerve behind it to send signals to the brain.
The brain then tries to decipher and interpret the sound.
Ultrasound
When a sound is louder than 20,000 Hz (20 kHz), it's called ultrasound. Bats are able to hear ultrasound as well as cats and dogs. Ultrasound is most commonly known for its use in medicine. We can use ultrasound scans to see a baby growing in the womb. We can also look into the body to help with other medical diagnoses.
Therapeutic ultrasound
Ultrasound can also be for therapy. It helps to treat a range of musculoskeletal issues. Physiotherapists use ultrasound to relieve pain as it is safe and non invasive.
Microphones
Another way to detect sound is to use a microphone. The microphone picks up vibrations just like our ears.
Instead of an eardrum, the microphone has a diaphragm which vibrates and sends electrical signals.
The next time you have a go at karaoke, think of the amazing science behind it!
Loudspeakers
Standing next to someone with a loudspeaker isn't the best idea.
The loudspeaker converts the vibrations of the person speaking and amplifies them, making them much louder!
Speakers you find in your car or at a music concert convert electrical energy into kinetic energy. The cone inside the speaker moves, creating sound waves.
Echooooo...
Have you ever shouted hello in a tunnel or big hall and heard a familiar reply? That sound you heard was an echo of your voice. Echos happens when soundwaves reflect off of surfaces similar to light refleting off a mirror. Smooth surfaces are great for reflecting soundwaves. Carpets and curtains will absorb soundwaves becuause of their softness, helping to dampen noise and minimise echoing.
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