Waves 1

Question 1

What does a progressive wave carry away from its source?

Answer 1

Energy

A progressive wave transfers energy without transferring material.

Question 2

What is the relationship between wave energy and electromagnetic waves?

Answer 2

Electromagnetic waves cause things to heat up.

Question 3

What effect do X-rays and gamma rays have on electrons?

Answer 3

They knock electrons out of their orbit, causing ionisation.

Question 4

What do loud sounds cause in air particles?

Answer 4

Large oscillations which can make things vibrate.

Question 5

What can wave power be used for?

Answer 5

To generate electricity.

Question 6

What is displacement in the context of waves?

Answer 6

How far a point on the wave has moved from its undisturbed position.

Question 7

Define amplitude in wave terminology.

Answer 7

The maximum magnitude of the displacement.

Question 8

What does wavelength represent?

Answer 8

The length of one whole wave cycle, e.g., from crest to crest or trough to trough.

Question 9

What is the period of a wave?

Answer 9

The time taken for a whole cycle (vibration) to complete.

Question 10

What does frequency measure?

Answer 10

The number of cycles (vibrations) per second passing a given point.

Question 11

How is phase defined in wave terminology?

Answer 11

A measurement of the position of a certain point along the wave cycle.

Question 12

What is phase difference?

Answer 12

The amount one wave lags behind another.

Question 13

How are phase and phase difference measured?

Answer 13

In angles (in degrees or radians).

Question 14

What is the formula that relates frequency and period?

Answer 14

Frequency = 1/Period.

Question 15

What is the unit of frequency?

Answer 15

Hertz (Hz).

Question 16

What is the wave speed equation?

Answer 16

Wave speed (v) = frequency (f) x wavelength (λ).

Question 17

What does a cathode ray oscilloscope (CRO) measure?

Answer 17

Voltage.

Question 18

What does the trace on an oscilloscope represent?

Answer 18

The displayed wave from a signal generator as a function of voltage over time.

Question 19

What are the two axes on an oscilloscope display?

Answer 19

Vertical axis in volts, horizontal axis in seconds.

Question 20

How can you find wave frequency using an oscilloscope?

Answer 20

By calculating the period from the trace and using the formula f = 1/T.

Question 21

If the timebase is set to 4.0 ms/div and one cycle takes 4 squares, what is the period?

Answer 21

16 ms.

Question 22

Calculate the frequency if the period is 16 ms.

Answer 22

62.5 Hz.

Question 23

What type of waves are all electromagnetic waves?

Answer 23

Transverse waves

Transverse waves have vibrations at right angles to the direction of travel.

Question 24

How can transverse waves be represented graphically?

Answer 24

Displacement against time and displacement against distance

Both representations often yield the same shape; check x-axis labels.

Question 25

What sign is given to displacements upwards from the center line in wave graphs?

Answer 25

+ sign

Question 26

What is the most common example of a longitudinal wave?

Answer 26

Sound wave

Question 27

What two phenomena alternate in a sound wave?

Answer 27

Compression and rarefaction

Question 28

Why can't sound travel through a vacuum?

Answer 28

It requires a medium to propagate

Question 29

How is intensity defined in the context of waves?

Answer 29

Rate of flow of energy per unit area at right angles to the direction of travel

Question 30

What is the formula for intensity?

Answer 30

Intensity = Power / Area

Question 31

Intensity is proportional to which aspect of a wave?

Answer 31

Amplitude squared

Question 32

How much energy is required to double the size of vibrations?

Answer 32

Four times as much energy

Question 33

At what speed do all electromagnetic waves travel in a vacuum?

Answer 33

3.00 × 10^8 m/s

Question 34

What do electromagnetic waves consist of?

Answer 34

Vibrating electric and magnetic fields

Question 35

What is the relationship between electric and magnetic fields in electromagnetic waves?

Answer 35

They are at right angles to each other

Question 36

What are the seven categories of the electromagnetic spectrum?

Answer 36

* Radio waves * Microwaves * Infrared * Visible light * Ultraviolet * X-rays * Gamma rays

Question 37

How does wavelength affect the behavior of electromagnetic waves?

Answer 37

Longer wavelengths exhibit more obvious wave characteristics

Question 38

Which type of electromagnetic wave has the highest energy?

Answer 38

Gamma rays

Question 39

What is the relationship between energy and frequency in electromagnetic waves?

Answer 39

Energy is directly proportional to frequency

Question 40

What is the approximate wavelength range for radio waves?

Answer 40

10^3 to 10^6 m

Question 41

What happens to matter when exposed to infrared waves?

Answer 41

Mostly absorbed, causing heating

Question 42

What type of penetration do X-rays have?

Answer 42

Absorbed by matter with slight ionisation

Question 43

What is one use of gamma rays in medicine?

Answer 43

To kill cancer cells

Question 44

Fill in the blank: Intensity is proportional to _______.

Answer 44

Amplitude squared

Question 45

True or False: All electromagnetic waves can be polarized.

Answer 45

True

Question 46

What is the definition of a polarised wave?

Answer 46

A polarised wave only oscillates in one direction ## Footnote Polarisation involves filtering out unwanted oscillations.

Question 47

What happens when waves pass through a vertical fence?

Answer 47

The wave will only get through if the vibrations are vertical ## Footnote This action filters out vibrations in other directions.

Question 48

What is the plane of polarisation?

Answer 48

The plane in which a wave vibrates ## Footnote For example, a rope wave can be polarised in the vertical plane.

Question 49

What is plane polarisation?

Answer 49

Polarising a wave so that it only oscillates in one direction

Question 50

What are ordinary light waves a mixture of?

Answer 50

Different directions of vibration ## Footnote The vibrating components are electric and magnetic fields.

Question 51

What does a polarising filter do?

Answer 51

It only transmits vibrations in one direction

Question 52

What occurs when two polarising filters are at right angles to each other?

Answer 52

No light will get through ## Footnote The intensity of light becomes zero.

Question 53

What is required to observe polarisation using two polarising filters?

Answer 53

Align the transmission axes of two polarising filters ## Footnote Shine unpolarised light on the first filter.

Question 54

What happens when the transmission axes of two filters are aligned?

Answer 54

All of the light that passes through the first filter also passes through the second

Question 55

As you rotate the second filter, what happens to the intensity of light?

Answer 55

The intensity decreases as the vertical component of the second filter's transmission axis decreases

Question 56

What is the intensity of light when the two transmission axes are at 45 degrees to each other?

Answer 56

Half that getting through the first filter

Question 57

What happens to light intensity when the two filters are rotated back to alignment after 180 degrees?

Answer 57

All light will be able to pass through the second filter again

Question 58

What is an application of polarising filters in 3D films?

Answer 58

The filters in each lens are at right angles to each other to create depth

Question 59

Why can't polarising filters be used on microwaves?

Answer 59

Their wavelength is too long

Question 60

What is used to polarise microwaves instead of polarising filters?

Answer 60

Metal grilles, which are squares full of metal wires aligned

Question 61

What is the maximum intensity of microwaves passing through a metal grille?

Answer 61

When the direction of vibration of the microwaves and the wires on the grille are at right angles

Question 62

What happens when the wires of the metal grille are aligned with the direction of the microwaves?

Answer 62

No signal will be shown on the voltmeter

Question 63

What effect does the vibrating electric field of the microwave have on the metal grille?

Answer 63

It excites electrons in the metal grille

Question 64

What happens to the energy of incoming microwaves when they hit the metal grille?

Answer 64

It is absorbed and re-emitted in all directions

Question 65

What does the microwave receiver only receive?

Answer 65

Microwaves in one plane

Question 66

What is the outcome when the wires and vibrations of the waves are aligned?

Answer 66

More electrons are excited, causing a drop in intensity