5.1 - Basic Waves

Question 1

What does a wave do

Answer 1

A wave is a means for transferring energy via oscillations

Whilst energy moves from one place to another, the waves cause no net movement of any matter

Question 2

What’s a mechanical wave

Answer 2

It’s a wave in which there needs to be some sort of material medium - a substance that oscillates to allow the transfer of energy

Question 3

What’s an electromagnetic wave

Answer 3

They can transfer energy through repeated oscillations of electric and magnetic fields, but these fields do not need matter to support them (unlike a mechanical wave)

The interaction between em wave and matter generally slows their transfer or energy - eg light travels more slowly in water than it does in a vacuum

Question 4

Tell me the 2 ways of graphing waves

Answer 4

Displacement (y) and distance travelled (x)

Or

Displacement (y) and time (x)

Both look like a transverse wave going up and down

Question 5

What does the displacement distance show

Answer 5

Shows the Physiical scale of the oscillations and the movement of energy

Question 6

What does the displacement time graph show

Answer 6

It shows how the wave vibrations occur over time

Question 7

Define wave displacement

Answer 7

The position of a particular point on a wave, at a particular instant in time, measured from the mean (equilibrium) position

Symbol is usually x, measured in metres

Question 8

What’s the wave amplitude

Answer 8

The magnitude of the maximum displacement reached by an oscillation in the wave

Symbol = A and measured in metres

Question 9

Define wave frequency

Answer 9

The number of complete wave cycles per second

This may sometimes be measured as the number of complete waves passing a point per second

Symbol = f and units hertz

Question 10

Define wavelength

Answer 10

The distance between a point on a wave and the same point on the next cycle of the wave
Eg peak to peak

Symbol = lander thing, units in metres

Question 11

Define the wave period

Answer 11

It’s the time taken for one complete oscillations at one point on the wave, this will also be the time taken for the wave to travel one wavelength

Symbol = T measured in seconds

Question 12

Define the wave phase

Answer 12

The stage a given point on a wave is through a complete cycle

Phase is measured in angle units, as a complete wave cycle is considered to be the same as traveling around a complete circle, that is 360 degreee or 2 pi radians

No standard symbol, measured in SI units rad

Question 13

Define the wave speed

Answer 13

The rate of movement of the wave - the same as speed in general

Symbol v or c for em waves and units m per second

Question 14

What’s the wave equation

Answer 14

Wave speed = frequency x wavelength

v = f x lander

Question 15

How can we investigate the speed of sound

Answer 15

We can use a twin beam oscilloscope to find the extra time a sound takes to travel a short extra distance - one beam trace shows a sound picked up by a microphone held 50cm roughly from the loud speaker

The other trace shows the same sound picked up by a second microphone held further from the loud speaker

The difference in positions of the peaks on oscilloscope shows the time taken for the sound to travel the extra distance this we can work out the speed v = d/t

Must synchronise the traces to minimis the effect of random error - make sure the traces are in phase and so that’s one wavelength so we can set frequency on signal generator and the. Use wave equation

Question 16

Tell me about pulse echo measurements

Answer 16

Bats use echolocation using very high frequency sound pulses, gives a much more detailed perception of the world at distances less than 5m
- doesn’t work far away

A sound pulse is sent out and is reflected by objects and a bat can measured the time to instinctively calculate the distance to the reflecting objects using d = s x t

Question 17

Tell me about human use of echo location

Answer 17

We have developed similar pulse echo ranging and imaging systems in a very wide range of technological applications from sonar on ships and submarines to air traffic control radar, medical imaging and the measurement of distance to asteroids and to the moon - it can avoid the need to land on the planet

Question 18

How do humans use similar pulse-echo ranging and imaging systems in a range of technological applications

Answer 18

We use it for sonar on ships and submarine to air traffic control radar, medical imaging and the measurement of distance to asteroids and to the moon

Oh lol this is the same as another question but I already typed it now so hav 2

Question 19

How can the time period / period of a wave be calculated

Answer 19

T = 1/ f

F = frequency

Question 20

What’s a transverse wave

Answer 20

It’s one where the movements of the particles, or fields in an electromagnetic wave, are up and down or left and right whilst the energy travels forwards

Question 21

What’s a longitudinal wave

Answer 21

In a fluid, eg air, the wave is generated by squashing particles together and then stretching them apart from eachother, repeatedly - thus vibrating them longitudinally

The areas of high pressure cause the particles to push apart from each other - making the particles move and squash their neighbours and so on - higher pressure is known as a compression

Where there are too few particles it’s a rarefaction

Question 22

How can we illustrate / graph longitudinal waves

Answer 22

We have to turn the numbers into numbers so we can draw it on a displacement distance graph so it looks like a transverse wave so we can get amplitude and wavelength from the graph

Question 23

What are sound waves caused by

Answer 23

Oscillations of particles of a medium, causing compressions and rarefactions along the line of movement of the wave

A compression occurs when particles either side are displaced towards it - displaced in opposite directions towards eachother

Question 24

What does an oscilloscope show

Answer 24

The vibrations over time

Question 25

Tell me about primary/ p waves

Answer 25

A type of seismic wave, faster than S waves

They are longitudinal as they push and pull as it travels

Question 26

Tell me about secondary / s wsves

Answer 26

They are transverse and shake from side to side as waves travel

Question 27

Define a transverse wave

Answer 27

It’s one in which the oscillations occur perpendicular to the direction of movement of wave energy

Question 28

Define a longitudinal wave

Answer 28

It’s one in which the oscillations occur parallel to the direction of movement of wave energy

Question 29

Define a compression

Answer 29

Is an area in a longitudinal wave in which the particle oscillations put them close to each other then their equilibrium state

Question 30

Define a rarefaction

Answer 30

Is an area in a longitudinal wave in which the particle oscillations put them future apart from eachother than their equilibrium state