Waves Flashcards by Anna Kunnel

What do waves do?

Waves transfer energy from one place to another without transferring any matter.

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In which direction do waves transfer energy?

Waves transfer energy in the direction they are travelling.

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What happens when waves travel through a medium?

The particles of the medium oscillate and transfer energy between each other.

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What happens to the particles of a medium when a wave travels through them?

The particles stay in the same place- only energy is transferred.

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What is the amplitude of a wave?

The maximum displacement of a point on the wave from it’s undisturbed position.

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What is the wavelength of a wave?

The distance between the same point of two adjacent waves.

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What is the frequency of a wave?

The no. of complete waves passing a certain point her second.
Measured in hertz (Hz).

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What is 1Hz equal to?

One wave per second.

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What is the time period of a wave?

The amount of time it takes for a full cycle of the wave.

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Draw a labelled diagram of a wave.

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What is the equation for time period?

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What are all waves?

Either transverse or longitudinal waves.

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How do the oscillations in a transverse wave behave?

The oscillations are perpendicular to the direction of energy transfer.

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What type of wave is most waves?

Transverse

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What are some examples of transverse waves?

All electromagnetic waves
Ripples and waves in water
A wave on a string

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What are some examples of longitudinal waves?

Soundwaves in air
Shock waves

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How do the oscillations in a longitudinal wave behave?

The oscillations are parallel to the direction of energy transfer.

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What is the equation for wave speed?

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What is wave speed?

The speed at which energy is being transferred.

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What happens when you attach a signal generator to a speaker.

You can generate sounds with a specific frequency.

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How can we use an oscilloscope to measure the speed of sound?

1) Set up the oscilloscope so the detected waves at each microphone are shown as separate waves.
2) Start with both microphones near the speaker, then slowly move one away until the two waves are aligned on the display, but have moved exactly one wavelength apart.
3) Measure the distance between the microphones to find one wavelength.
4) You can then use the formula ‘v= f x wavelength’ to find the speed of the sound waves passing through the air- the frequency is whatever you set the signal generator (usually around 1kHz).
5) The speed of sound in air is around 330m/s, so check your results roughly agree with this.

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Draw a diagram of the set up of the experiment where we measure the speed of sound.

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How can we measure the speed of water ripples using a lamp?

1) Use a signal generator attached to the dipper of a ripple tank to create water waves at a set frequency.
2) Use a lamp to see wave crests on a screen below the tank. Make sure the size of the waves’ shadows are the same size as the waves.
3) The distance between each shadow line is equal to one wavelength. Measure the distance between shadow lines that are 10 wavelengths apart, then divide this distance by 10 to find the average wavelength. This is a good method for measuring small wavelengths.
4) If your struggling to measure the distance, you could take a photo of the shadows and ruler and find the wavelength from the photo instead.
5) Use ‘ v = f x wavelength’ to calculate the wave speed of the waves.
6) This set up is suitable for investigating waves, because it allows you to measure the wavelength without disturbing the waves.

Draw a diagram of the set up of the experiment where we measure the speed of water ripples.

How can we measure the speed of waves on strings?

1) Set up equipment properly. 2) Turn on the signal generator and vibration transducer. The string will start to vibrate. 3) Adjust the frequency of the signal generator until there's a clear wave on the string. The frequency you need will depend on the length of string between the pulley and the transducer, and the masses you've used. 3) You need to measure the wavelength of these waves. The best way to do this accurately is to measure the lengths of around four or five half-wavelengths in one go, then divide to get the mean half-wavelength. You can then double this mean to get a full wavelength. 4) The frequency of the wave is whatever the signal generator is set to. 5) You can find the speed of the wave using the ' v = f x wavelength' equation.

Draw a diagram of the set up of the experiment where we measure the speed of waves on strings.

What three things can happen when a wave arrives at a boundary between two different materials?

The wave will be absorbed, transmitted or reflected.

What happens when a wave is absorbed by the material the wave is trying to cross into?

This transfers energy to the material's energy stores.

What happens when a wave is transmitted?

The wave carries on travelling through the new material. This often leads for refraction.

What controls how a wave behaves when it arrives at the boundary of two materials?

The wavelength of the wave The properties of the materials involved

What is a ray?

Its a line showing the path a wave travels in. They are always drawn as straight lines.

What is the rule for all reflected waves?

The angle of incidence = the angle of reflection

Draw a simple ray diagram for reflection.

What are the two different types of refelction?

Specular and diffuse

What is specular reflection?

When a wave is reflected in a single direction by a smooth surface.

What is diffuse reflection?

When a wave is reflected by a rough surface and the reflected rays are scattered in lots of different directions.

Why does diffuse reflection happen?

The normal is different for each incoming ray, which means that the angle of incidence is different for each ray. The incidence-reflection angle rule still applies.

Draw a diagram of specular reflection.

Draw a diagram of diffuse reflection.

What happens when light is reflected from a rough surface?

The surface appears matte and you don't get a clear reflection of objects.

What type of wave are EM waves?

Transverse waves

What do EM waves do?

Transfer energy from a source to an absorber e.g. a hot object transfers energy by emitting infrared radiation, which is absorbed by the surrounding air.

What speed do EM waves travel at?

They all travel at the same speed through air or a vacuum- 3 x 10^8 m/s.

What do EM waves form?

A continuous spectrum over a range of frequencies.

How are EM waves grouped?

They are grouped into seven basic types, based on their wavelength and frequency.

EM waves aren't vibrations of particles, instead they're vibrations of...

electric and magnetic fields. This means they can travel through a vacuum.

Why is there such a large range of frequencies in the EM spectrum?

EM waves are generated by a variety of changes in atoms and their nuclei e.g. changes in the nucleus of an atom created gamma rays. This is also explains why atoms cab absorb a range of frequencies- each one causes a different change.

Name all the EM waves in order of increasing frequency and decreasing wavelength.

Radio waves Microwaves Infra red Visible light Ultraviolet X-rays Gamma rays

Why are different EM waves used for different purposes?

Because of their different properties.

What are some uses of radio waves?

Communication Broadcasting

How can we communicate using radio waves?

Using an oscilloscope, transmitter and receiver, we can transfer information of any kind.

What are the three types of radio waves?

Long wave Short wave Very short wave

What can long wave radio waves do?

They can transfer huge distances without having to interact with anything along the way. This is because they diffract/bend around the curved surface of the Earth. These waves are great for long-range communication.

What can short wave radio waves do?

Can travel long distances. They're reflected from the ionosphere and by bouncing back and forth repeatedly they can cover long distances. These waves can also be used to send data over short distances e.g. for Bluetooth.

What can very short radio waves do?

These are used for FM radio and TV. These waves have to travel directly from the transmitter to the receiver. Surrounding structures can get in the way of that direct transmission.