Section 3: Waves Flashcards
What is a progressive wave?
It carries energy from one place to another without transferring any material.
How is a wave caused?
A wave is caused by something particles or fields oscillate at a source. These oscillations pass through the medium as the wave travels, carrying energy with it.
How can we tell that waves carry energy?
Electromagnetic waves cause things to heat up.
X-rays and gamma rays knock electrons out of their orbits, causing ionisation.
Loud sounds cause large oscillations of air particles, which can make things vibrate.
Wave power can be used to generate electricity.
What is reflection of a wave?
The wave is bounced back when it hits a boundary.
What is refraction of a wave?
The wave changes direction as it enters a different medium. The change in direction is a result of the wave slowing down or speeding up.
What is diffraction of a wave?
The wave spreads out as it passes through a gap or round an obstacle.
What is meant by the displacement of a wave?
How far a point on the wave has moved from its undisturbed position.
What is meant by the amplitude of a wave?
The maximum magnitude of displacement.
The distance from the undisturbed position to a crest or trough of the wave
What is meant by the wavelength of a wave?
The length of one whole wave oscillation or wave cycle.
The distance between 2 adjacent points in phase on a wave.
What is meant by the period of a wave?
The time taken from one whole wave cycle to go from its highest point and back to its highest point again.
The time taken for one complete oscillation or cycle.
What is meant by the frequency of a wave?
The number of whole wave cycles (oscillations) per second passing a given point.
What is meant by the phase of a wave?
A measurement of the position of a certain point along the wave cycle.
What is meant by phase difference?
The amount by which one wave lags behind another wave.
What can phase and phase difference be measured in?
In angles in degrees or radians.
In fractions of a cycle
How are frequency and time period linked to each other?
f=1/T
What is the unit for frequency?
Hertz ( Hz )
What equations can you use to find wave speed?
v=d/t
c=f x lamda
What is the speed of light in a vacuum?
3x10^8
What is a method of measuring the speed of sound?
Use two microphones in a straight line a distance apart. The microphones should have separate inputs so the signals from each can be recorded separately.
Use the signal generator to produce a sound from the loudspeaker and use the computer to record the time between the first and second second microphone picking up the sound. Do this by measuring the time delay between the first peak of the signal received by each microphone in a graph of voltage against time.
You can then use speed=distance/time to calculate the soles of the sound waves.
You should repeat this experiment multiple times and take averages of your results.
What is the method of measuring wave speed in water?
Set up a ripple tank.
Start by recording the depth of water in the tank using a ruler.
Use the ripple tank dipped to create vibrations with a regular frequency in the tank. Dim the main lights in the room and turn on the strobe light.
Increase the french if the strobe light from zero until the waves appear to be standing still. When this happens, the frequency of the strobe light is equal to the frequency of the water waves.
Use a ruler on the white paper below the tank to measure the distance between two adjacent peaks. You could make this measurement more precise by measuring the distance between several peaks and dividing this by the number of troughs in between. This distance between two adjacent peaks is equal to the wavelength so you can use the french and wavelength to find the speed.
Repeat this experiment for a range of water depths, measuring the wavelength and calculating the wave sped each time.
You should observe that the waves travel quicker in deeper water.
What is a transverse wave?
The displacement of the particles is at right angles to the direction of energy propagation.
What are some examples of transverse waves?
All electromagnetic waves
Ripples on water
Waves on strings
S-waves from earthquakes
What are longitudinal waves?
The displacement of the particles is along the direction of energy propagation.
What are some examples of longitudinal waves?
Sound
Primary waves from earthquakes