P12- Wave properties

Question 1

Mechanical waves
Examples?
Key feature?
What type?

Answer 1

Sound waves, water waves, seismic waves
Travel through a medium
Can be transverse or longitudinal

Question 2

Electromagnetic waves
Examples?
Key feature?
What type?

Answer 2

Light waves, radio waves microwaves
Can travel through a vacuum (no medium is needed)
All are transverse waves

Question 3

What do waves transfer?

Answer 3

Energy and information without transferring matter, as the substance itself doesn’t travel

Question 4

Transverse waves
Direction of oscillations?

Answer 4

The oscillations are perpendicular to the direction of the energy transfer

Question 5

Longitudinal waves
Direction of oscillations?

Answer 5

The oscillations are parallel to the direction of the energy transfer

Question 6

Amplitude
Def?
How does it relate to energy?
Where is it on a graph?

Answer 6

The maximum displacement of a point of a wave from its rest position
The bigger the amplitude, the more energy it carries
Difference between rest and peak

Question 7

Wavelength
Def?
Wave speed
Def?

Answer 7

Distance from one point on a wave to another (trough to trough or peak to peak)
Distance travelled by each wave every second through a medium

Question 8

Frequency
Def?
Unit?
Period?
Calculation?

Answer 8

Number of waves passing a fixed point every second
hertz (Hz)
Time taken for each wave to pass a fixed point
period (s) = 1 / frequency

Question 9

Measuring the speed of sound in the air

Answer 9

Person A stands at a long, measured distance from Person B, but still in sight, they crash two cymbals together and Person B times the interval between seeing it and hearing it. Calculate speed using speed= distance/ time

Question 10

Refraction def?

Answer 10

Change in direction of a wave when crossing a boundary between one medium and another

Question 11

What happens to a plane wave when it crosses a boundary at an angle?

Answer 11

Each wave changes speed, wavelength and direction, but has the same frequency

Question 12

Plane waves when reflected from a straight barrier
Key fact and why?

Answer 12

Reflected at same angle because speed and wavelength doesn’t change

Question 13

What happens to a substance when waves are directed at it?

Answer 13

Some or all of the wave may be reflected. Substance can be heated as it gains energy from the absorbed waves

Question 14

Law of reflection

Answer 14

Angle of incidence= angle of reflection

Question 15

Specular reflection
Diffuse reflection

Answer 15

Smooth, flat surface and creates a virtual image
Rough surface, light scattered in all directions

Question 16

Density affecting waves?

Answer 16

The denser the object, the more slowly light passes through it

Question 17

How to find the frequency of waves from a ripple tank?

Answer 17

Count the number of waves passing through a point in 10 seconds and divide no of waves by 10.

Question 18

How to find wavelength, frequency and wave speed in a ripple tank?

Answer 18

-Sheet of white card under tank
-Adjust rod to touch surface of water
-Switch and adjust lamp and motor until pattern is shown
-Measure total length of pattern, and divide by no of waves to find wavelength
-Count no of waves passing a point in 10s and divide no of waves by 10 to find frequency
-Use wave speed= frequency x wavelength

Question 19

How to find wavelength, frequency and wave speed on a string?

Answer 19

-Set up string suspended between a bridge and generator
-Switch on signal generator, adjust tension of spring until it shows a pattern
-Use ruler to measure length between bridge and generator
-Divide total length by no of half waves
-Multiply by 2 to find wavelength
-Frequency shown by signal generator
-Use wave speed= frequency x wavelength

Question 20

Investigating wave speed practical

Answer 20

-Fill tray with small amount of water
-Gently drop one side
-Measure distance the wave travels and time it takes
-Calculate speed= distance / time

Question 21

High frequency=?
High amplitude=?

Answer 21

High pitch
High volume

Question 22

The ear
Can hear between what frequency range?
How do we hear?
Why is human hearing limited?

Answer 22

20-20,000 kHz
Sound waves make ear drum vibrate, send signals to brain
The conversion of sound waves to vibrations of solids only work up to a frequency range

Question 23

Ultrasound waves

Answer 23

Sound waves with a frequency greater than 20,000 Hz, so humans can’t hear

Question 24

What is echo sounding and what is it used for?

Answer 24

Using high-frequency sound waves to detect objects in deep water or depth below ship

Question 25

How do ultrasound scanners work?

Answer 25

Ultrasound waves are partially reflected from tissue boundaries and returns at different times to build an image of tissue boundaries on a screen.

Question 26

2 advantages of using ultrasound waves?

Answer 26

-Can scan organs and other tissues in the body
-Non-ionising, so is harmless

Question 27

Layer of the Earth and their states of matter?

Answer 27

Inner core= solid
Outer core= liquid
Mantle= solid
Crust= solid

Question 28

Seismic waves

Answer 28

Waves that travel through the Earth

Question 29

Def
Focus?
Epicentre?

Answer 29

Where an earthquake originates from
The nearest point on the surface to the focus

Question 30

2 types of seismic waves?
also called?
type of waves?

Answer 30

Primary waves (P-waves)– longitudinal
Secondary waves (S-waves)– transverse

Question 31

Primary waves and secondary waves
Cause?
What do they do?

Answer 31

Initial tremors that last around 1 min, push or pull on material
Tremors a few minutes later, shake the material from side to side

Question 32

P and S waves when in the Earth?
3 key facts

Answer 32

-Both bend as travel through mantle, change in speed due to changing depth, so direction changes
-P-waves refract at mantle and outer core boundary
-S-waves can’t travel through liquid outer core