Waves Flashcards
How do waves transfer energy?
When waves travel through a medium the particles of the medium oscillate and transfer energy between each other.
What is the amplitude of a wave?
This is the maximum displacement of a point on the from its undisturbed position
What is wavelength?
This is the distance between the same point on two adjacent waves
What is the frequency of wave?
This is the number of complete waves passing a certain point per second it is measured in Hertz, Hz
How do you find the period of a wave?
This is the amount of time it takes for a full cycle of the wave
T=1/f
Period = 1/frequency
What is a transverse wave?
This is where the oscillations are perpendicular to the direction of energy transfer.
What is a longitudinal wave?
This is where the oscillations are parallel to the direction of energy transfer
Give some examples of a transverse wave
All electromagnetic waves
Ripples and waves in water
A wave on a string
Give some examples of a longitudinal wave
Sound waves in air, ultrasound
Shock waves - seismic waves
What is wave speed?
This is the speed at which energy is being transferred
What is the equation for wave speed?
Wave speed=frequency*wavelength
v=f*wavelength
How would you measure waves?
Oscilloscope
Water ripples
Strings
How would you measure sound waves?
Set up two microphones and an oscilloscope to find the wavelength of the sound waves generated. Slowly move one microphone away until the two waves are aligned on the display. Measure the distance between the microphones to find one wavelength. Then use the formula V=f*wavelength to find speed. The frequency is whatever you set the signal generator to.
How would you measure the speed of water ripples?
Use a signal generator attached to a dipper of a ripple tank you can create waves at a set frequency. Use the lamp to see the water ripple below the tank. Measure the distance between the shadow lines from a picture that are ten wavelengths apart then divide this by ten to find the average. Use V=f*wavelength.
How would you find wave speed of a string?
Use a generator and vibration transducer to keep a steady wave to form on the string. Measure the wavelength of these waves through a photo measure four or five half wave lengths then divide by that number then double it. Use the wave speed equation.
Give some properties of waves
Waves can be absorbed, transmitted or reflected, when a wave arrives at a boundary.
What is the simple rule of reflected waves?
Angle of incidence=angle of reflection
What is diffuse reflection?
This is where a wave is reflected by a rough surface and the reflected waves are scattered in lots of different directions. When light is reflected by a rough surface the surface appears matte and you don’t get a clear reflection/ image of objects.
What are electro-magnetic waves?
They are transverse waves that transfer energy from a source to an absorber. All EM waves travel at the same speed through air or a vacuum.
What are the forms of EM waves?
Radio waves Micro waves Infra red waves Visible light waves Ultra voilet X-rays Gamma rays They each have different frequencies and properties so they are used differently.
What is refraction?
This is where the wave changes direction when it crosses a boundary. The angle at which it is refracted depends on how much the wave speeds up or slows down which usually depends on the density of the two materials. When the wave slows it bends towards the normal and when it speeds up it bends away from the normal.
What are EM waves made up of?
Oscillating electric and magnetic fields. Alternating current are made up of oscillating charges.
What are the uses of radio waves?
They are used for communication, This is because long wavelengths diffract around curved surfaces. This makes it possible to receive the wave even if you cannot see the transmitter. However, short radio waves can also be received at long distances due to them being reflected from the ionosphere - an electrically charged layer in the Earths upper atmosphere.
What are micro wave rays used for?
- They are used in ovens, the microwaves need to be absorbed by water molecules. The microwaves penetrate a few centimetres into the food before being absorbed and transferring the energy they are carrying causing the water to heat up.
- They are also used for communicating with satellites in space because microwaves can pass through the earths atmosphere without being reflected or refracted.
What is infra red waves used for?
They are used to increase and monitor temperature. The hotter the object the more infra red radiation is given off.
They are used in toasters heating element.
How does a fibre optic cable work?
They are thin glass or plastic fibres that can carry data over long distances as pulses of visible light. They work because of reflection, the light rays are bounced back and forth until they reach the end of the fibre.
What are some uses for ultraviolet rays?
- Fluorescent colour.
- Fluorescent lights
- Security devices, some things invisible will show under the light
- It can be used to get a suntan,
What are X-rays used for?
They are used to take photographs of you’re bones to see if there is and breaks or fractures.
How do x-rays work?
The x-rays pass through flesh easily but not so easily through dense materials such as bone or metal - the amount of radiation that’s absorbed gives you an x-ray image.
How are gamma rays used in treating cancer patients?
High doses of these rays and x-rays means living cells will die - so they are carefully directed to cancer cells in small amounts which focus on the cancer cells, avoiding healthy tissue (radiotherapy).
