Module 4 - Section 2 - Wave Basics Flashcards
What are the 2 types of waves ? And what are they ?
Mechanical waves - are vibrations that travel through a medium ( a substance ) - Sound waves, water waves, waves on a spring and ropes and seismic waved produced by earthquakes
Electromagnetic waves - Can all travel through a vacuum at the speed of 300 000 km/s - can travel through a vacuum meaning that no medium is needed - light waves, radio waves and microwaves
What is a progressive wave and what does it do ?
A progressive wave is a moving wave - it carries energy from one lace to another without transferring any material - the transfer of energy is in the same direction as the wave is travelling
In what direction is the direction of energy transfer ?
Energy transfer is in the same direction as the wave is travelling
What are some ways you can tell that waves transfer energy ?
1) electromagnetic waves cause things to heat up ( think UV rays - suntan )
2) X-rays and gamma rays knock electrons out of their orbits - causing ionisation
3) Loud sounds cause large oscillations in air particles which can make things vibrate
4) Wave power can be used to generate electricity
What is displacement ? And what’s the units ? And what’s the symbol ?
Displacement is how far a point on a wave has moved from its undisturbed position
Symbol = x
Units = metres, m
Whats amplitude ? Whats the units and the symbol ?
Amplitude is the maximum magnitude of the displacement
Symbol - A
Unit - metres
What does a wave do ?
A wave transfers energy away from its source
What is wavelength and what is the unit ?
Wavelength is the length of one whole wave cycle e.g. from crest to crest or trough to trough
The unit for wavelength is landa (m)
What is the period of a wave and what are the units ?
The period of a wave - is the time taken for a whole cycle ( one oscillation - vibration ) to happen ( to be complete )
The unit is Time - measured in secs
What is a phase ?
A phase is a measurement of the position of a certain point along the wave cycle
So it’s literally the measurement of the position on a what could be a random point on a wave which could be measured in radians and degrees
What is phase difference ?
It’s how much one wave lags behind another - the difference in the phase angle between 2 waves
Whats phase and phase difference measured in?
They are measured in radians and degrees
What is frequency ?
The frequency is the inverse of a period
f = 1 / T
Whats the equation for the speed of a wave ?
Speed of a wave = frequency x wavelength
What does an oscilloscope do ?
An oscilloscope is used to display waves
How does a CRO ( cathode ray oscilloscope ) work ?
A CRO measures voltage and then it displays waves from a signal generator as a function of voltage over time
Whats the displayed wave on the CRO called ?
It’s called a trace
What is the screen of an oscilloscope split into ?
The screen I split into squares called divisions - the vertical axis is in volts ( and it means volts per division ) and the horizontal axis is in seconds ( and it means seconds per division ) also known as timebase
What does the gain dial on the oscilloscope do ?
The volts per division is controlled by the gain dial
What does the time base dial do ?
The time base dial controls the seconds per division which is on the x axis
What can you do if it’s hard to read off the measurements on an oscilloscope ?
Then you can alter the gain and timebase dial to make it easier
How come you get different traces depending on the source on an oscilloscope ?
If you plug in an AC supply into a oscilloscope, you get a trace that goes up and down in a regular pattern - sometimes its positive and sometimes its negative
A microphone converts sound waves into electrical signals which can be seen on a oscilloscope
What does a microphone do ?
It converts sound waves into electrical signals which can be seen on a oscilloscope
What does each square of an oscilloscope represent ?
It represents a division
