Chapter 12 Wave Properties

Question 1

12.1 What are waves?

Answer 1

They can be used to transfer energy and information.

Question 2

12.1 What are mechanical waves?

Answer 2

These waves need a medium to travel through. They can be transverse or longitudinal waves.
Examples are: sound waves, water waves and seismic waves.

Question 3

12.1 What are transverse waves?

Answer 3

Transverse waves oscillate perpendicular to the direction of energy transfer of the waves. Ripples on the surface of water are transverse waves. So are all electromagnetic waves.

Question 4

12.1 What are longitudinal waves?

Answer 4

Longitudinal waves oscillate parallel to the parallel to the direction of energy transfer of the waves. Sound waves in air are longitudinal waves.

Question 5

12.1 What are electromagnetic waves?

Answer 5

Waves that can pass through a vacuum and no medium is needed.

Question 6

12.2 What is the amplitude of a wave?

Answer 6

The maximum displacement of a point on the wave from its undisturbed position. On a diagram, it is the displacement from the middle to the peak.

Question 7

12.2 What happens to the energy when the amplitude increases?

Answer 7

The bigger the amplitude of the waves, the more energy the waves carry.

Question 8

12.2 What is the wavelength?

Answer 8

The wavelength of a wave is the distance from a point on the wave to the equivalent point on the adjacent wave. It is from one peak (the top of the wave) to another or from one trough (the bottom of the wave) to another.

Question 9

12.2 What is the frequency of a wave?

Answer 9

The number of waves passing a fixed point every second is called the frequency of the waves.

Question 10

12.2 What is the period of a wave? And equation

Answer 10

The period of a wave is the time taken for each wave to pass a fixed point.
Period (seconds) = 1/frequency (hertz)

Question 11

12.2 What is the speed of a wave?

Answer 11

The speed of the wave is the distance travelled by each every second through a medium.

Question 12

12.2 What is the wave speed equation in terms of frequency x wavelength

Answer 12

Wave speed = frequency x wavelength

Question 13

12.3 How can reflection be understood by the ripple tank?

Answer 13

Plane waves in a ripple tank are reflected from a straight barrier at the same angle to the barrier as the incident waves because their speed and wavelength do not change on reflection.

Question 14

12.3 What does refraction mean?

Answer 14

Refraction of waves is the change of the direction in which they are travelling when they cross a boundary between one medium and another medium.

Question 15

12.3 How can refraction be shown?

Answer 15

Plane waves crossing a boundary between two different materials are refracted unless they cross the boundary at normal incidence.

Question 16

12.3 What happens at a boundary?

Answer 16

Waves can transmitted or absorbed.

Question 17

12.4 What are sound waves?

Answer 17

Sound waves are vibrations that travel through a medium

Question 18

12.4 What can sound waves not do?

Answer 18

They cannot travel through a vacuum

Question 19

12.4 How can you investigate sound waves?

Answer 19

• A ripple tank for water waves
• A stretched spring for waves in a solid
• A signal generator and a loudspeaker for sound waves.

Question 20

12.5 What happens when you increase the pitch of a note?

Answer 20

The pitch of a note increases if the frequency of the spund waves increases

Question 21

12.5 How is the loudness of a sound wave increases?

Answer 21

The loudness of anote increases if the amplitude of the sound waves increases

Question 22

12.5 How do sound waves make humans hear things?

Answer 22

Sound waves cause the ear drum to vibrate, and the vibrations send signals to the brain.

Question 23

12.5 Why is human hearing limited?

Answer 23

The conversion of sound waves to vibrations of solids only works over a limited frequency range, so human hearing is limited.

Question 24

12.6 What are ultrasound waves?

Answer 24

They are sound waves of frequency above 20kHz

Question 25

12.6 How are ultrasound waves partly reflected?

Answer 25

They are partly reflected at a boundary between two different types of body tissue.

Question 26

12.6 How can tou calculate the distance of ultrasound waves?

Answer 26

They are reflected at boundaries and are timed, the timings are used to calculate distances.

Question 27

12.6 Why are ultrasound waves safer than X-rays?

Answer 27

They are non-ionising so it is safer than an x-ray

Question 28

12.6 Distrance travelled by a wave (ultrasound)

Answer 28

Distance travelled by the wave (m) = speed of ultrasound waves in body tissue (m/s) x time taken (s)

Question 29

12.6 The depth of the boundary below the surface for ultrasound waves equation

Answer 29

1/2 x speed of the ultrasound wave x time taken

Question 30

12.7 What are seismic waves

Answer 30

Waves that travel through the Earth

Question 31

12.7 How are seismic waves produced?

Answer 31

They are produced in an eathquake and spread out the epicentre

Question 32

12.7 What are primary waves?

Answer 32

These cause tremors lasting about one minute. These are longitudinal waves that push or pull on materials as they move through the Earth

Question 33

12.7 What are secondary waves?

Answer 33

They cause tremors a few minutes later. They are transverse waves that travel slower than P-waves. They shake the material that they pass through inside the Earth from side to side.

Question 34

12.7 What are L-waves

Answer 34

Most violent move,ents are caused by this and they usually arrive last. They travel slower but occur in the crust.

Question 35

12.7 What is the structure of Earth?

Answer 35

Solid inner core
Surrounded by a liquid outer core
Which is surrounded by the Earth’s mantle
The mantle is surrounded by the Earth’s crust