Module 4 - Section 2 - Wave Basics

Question 1

What are the 2 types of waves ? And what are they ?

Answer 1

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

Question 2

What is a progressive wave and what does it do ?

Answer 2

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

Question 3

In what direction is the direction of energy transfer ?

Answer 3

Energy transfer is in the same direction as the wave is travelling

Question 4

What are some ways you can tell that waves transfer energy ?

Answer 4

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

Question 5

What is displacement ? And what’s the units ? And what’s the symbol ?

Answer 5

Displacement is how far a point on a wave has moved from its undisturbed position

Symbol = x

Units = metres, m

Question 6

Whats amplitude ? Whats the units and the symbol ?

Answer 6

Amplitude is the maximum magnitude of the displacement

Symbol - A

Unit - metres

Question 7

What does a wave do ?

Answer 7

A wave transfers energy away from its source

Question 8

What is wavelength and what is the unit ?

Answer 8

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)

Question 9

What is the period of a wave and what are the units ?

Answer 9

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

Question 10

What is a phase ?

Answer 10

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

Question 11

What is phase difference ?

Answer 11

It’s how much one wave lags behind another - the difference in the phase angle between 2 waves

Question 12

Whats phase and phase difference measured in?

Answer 12

They are measured in radians and degrees

Question 13

What is frequency ?

Answer 13

The frequency is the inverse of a period

f = 1 / T

Question 14

Whats the equation for the speed of a wave ?

Answer 14

Speed of a wave = frequency x wavelength

Question 15

What does an oscilloscope do ?

Answer 15

An oscilloscope is used to display waves

Question 16

How does a CRO ( cathode ray oscilloscope ) work ?

Answer 16

A CRO measures voltage and then it displays waves from a signal generator as a function of voltage over time

Question 17

Whats the displayed wave on the CRO called ?

Answer 17

It’s called a trace

Question 18

What is the screen of an oscilloscope split into ?

Answer 18

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

Question 19

What does the gain dial on the oscilloscope do ?

Answer 19

The volts per division is controlled by the gain dial

Question 20

What does the time base dial do ?

Answer 20

The time base dial controls the seconds per division which is on the x axis

Question 21

What can you do if it’s hard to read off the measurements on an oscilloscope ?

Answer 21

Then you can alter the gain and timebase dial to make it easier

Question 22

How come you get different traces depending on the source on an oscilloscope ?

Answer 22

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

Question 23

What does a microphone do ?

Answer 23

It converts sound waves into electrical signals which can be seen on a oscilloscope

Question 24

What does each square of an oscilloscope represent ?

Answer 24

It represents a division