Topic Six - Waves Flashcards
(38 cards)
What is amplitude?
It is the maximum displacement of a point on the wave from its undisturbed position.
What is wavelength?
The distance between the same point on two adjacent waves.
Trough to trough.
What is frequency?
The number of complete waves passing a certain point per second.
What is frequency measured in?
Hertz
What is a period of a wave?
The amount of time it takes for a full cycle of the wave to pass a point.
What is a transverse wave?
The vibrations are perpendicular to the direction of the energy transfer.
What are examples of transverse waves?
Electromagnetic waves, light
Ripples and waves in water
A wave on a spring.
What are longitudinal waves?
The vibrations are prallel to the direction of energy transfer.
What are wavelengths in longitudinal waves?
From compression to compression
What are compressions in longitudinal waves?
When the spring tightens.
What are rarefractions in longitudinal waves?
When the spring stretches.
What are examples of longitudinal waves?
Sound waves in air
Shock waves-seismic waves
How can you measure the speed of sound?
Set up the oscilloscope so the detected waves at each microphone are shown as separate waves.
Start with both microphones next to the speaker then slowly move one away until the two waves are aligned on the display, but have moved exactly one wavelength apart.
Measure the distance between the microphones to find one wavelength.
How can you measure the speed of water ripples using a lamp?
Dim the lights and turn on the lamp.
Youll see a wave pattern made by the shadows of the wave crests on the screen below the tank.
The distance between each shadow length is equal to one wavelength.
Measure the distance between shadow lines that are ten wavelengths apart then divide it by ten to find an average wavelength.
Use the equation to find the speed of the waves.
How can you find the speed of waves on springs?
Turn on the signal generator and vibration transducer. The string will start to vibrate.
To change the length of the wave adjust the frequency on the signal generator.
Keep adjusting it until there is a clear wave on the string.
The frequency needed will depend on the length of the string between the pulley and the transducer.
Measure the wavelength of the wave. Do this by measuring all the half wavelengths on the string in one go, then divide by the number of half wavelengths and times by two to get the full wavelength.
What is refraction?
When light waves are bent when they enter a new material.
What happens when a wave arrives at the boundary of two different materials?
The wave can be absorbed by the second material.
Transfers energy to the materials energy stores, often a thermal energy store.
The wave is trasmitted through the second materials. It carries on travelling through the new material which often leads to refraction.
The wave is reflected-this is where the incoming wave is neither absorbed nor transmitted but instead is sent back away from the second material.
What is optical density?
A measure of how quickly light can travel through it.
The higher the optical density, the slower a wave travels through it.
What happens during refraction?
When a wave crosses a boundary between two materials it changes speed.
It the wave is travelling along the normal it will change speed but its not refracted.
If a wave hits the boundary at an angle it changes direction-its refracted.
If a wave bends towards the normal it slows down but if it bends away from the normal it speeds up.
How much is refracted depends on the density of the two materials.
How are radio waves made?
Alternating currents are made up of oscillating charges.
As the charges oscillate they produce electromagnetic waves.
The frequency of the waves produced will be equal to the frequency of the alternating current.
You can produce radiowavrd using the aternating current.
Th electrons oscillate to create the radio waves is called a transmitter.
When the radio waves reach the reciever they are absorbed.
The energy transferred by the waves is transferred to the electrons in the material of the reciever.
The energy causes the electrons to oscillate and the reciever generates an alternating current.
What happens to long wave radio waves?
They can be transmitted from all around the world.
That is because the long wavelengths diffract around the curved surface of the earth.
How are microwaves used by satellites?
Satellites.
The signal from a transmitter is transmitted into space.
It is where its pickef up by the satellite reciever dish orbiting above the earth.
The satellite transmits the signal back to earth in a different direction where its recieved by a satellite dish on the ground.
How are microwaves used in microwave ovens?
The microwaves need to be absorbed by water molecules in food so they use a different wavelength to satellites.
The microwaves penetrate a few cm into the food before being absorbed and transferring the energy they are carrying to the water molecules causing the water to heat up.
The water molecules transfer energy to the redt of the molecules in the food by heating which quickly cooks the food.
How is infrared radiation used to moniter temperature?
Infrared radiation is given out by all objects so the hotter the object the more IR radiation it gives out.
Infrared cameras can be used to detect infrared radiation and monitor temperature.
The camera detects the IR radiation and turns it into an electric signal, which is displayed on a screen.
The hotter an object the brighter it appears.
