Chapter 12 - Wave Properties

Question 1

What is a wave?

Answer 1

A wave is a transfer of energy from one point to another

Question 2

What are the 2 types of wave?

not transverse and longitudinal

Answer 2

Mechanical waves
Electromagnetic waves

Question 3

What is a mechanical wave?

Answer 3

Waves that vibrate through a medium (a substance)

Question 4

What is an electromagnetic wave?

Answer 4

Waves which can travel through a vacuum (no medium needed)

Question 5

Give an example of a mechanic and an electromagnetic wave

Answer 5

Mechanic - Sound
Electromagnetic - Light

Question 6

What is a transverse wave?

Answer 6

The oscillations of a transverse wave are perpendicular to the direction in which the waves transfer energy

Question 7

What is a longitudinal wave?

Answer 7

The oscillations of a longitudinal wave are parallel to the direction in which the waves transfer energy

Question 8

‘from its undisturbed position’

What is the amplitude?

Answer 8

The maximum displacement of a point on the wave from its undisturbed position

Question 9

What is the wavelength?

Answer 9

The distance from a point on the wave to the equivalent point on the adjacent wave

Question 10

The bigger the amplitude…

Answer 10

the more energy the waves carry

Question 11

What is frequency?

Answer 11

Frequency is the number of waves passing a fixed point every second

Question 12

What is the equation linking frequency and time period?

Answer 12

Period (s) = 1/frequency (Hz)

Question 13

What is the equation linking wave speed, frequency and wavelength?

Answer 13

Wave speed (m/s) = frequency (Hz) x wavelength (m)

Question 14

The angle of incidence is…

Answer 14

equal to the angle of reflection

Question 15

What can happen to a light wave when it reaches a boundary between 2 materials?

3 things can happen

Answer 15

Light can be:
- Reflected
- Transmitted (this includes being refracted)
- Absorbed

Question 16

The human ear can hear between _______________ and _______________

Answer 16

20 Hz and 20kHz

Question 17

What is ultrasound used for?

3 examples

Answer 17

• Pre-natal scanning (pregnancy)
• Cleaning jewellery
• Breaking down kidney stones

Question 18

What happens when ultrasound waves are sent to scan organs with an ultrasound transducer?

Answer 18

-The transducer emits a signal
-After a short time it receives a signal back
-This is caused by the ultrasound reflecting off the front of the organ

Question 19

If a signal from ultrasound is received after a longer time, what does that tell you about the object it reflected off?

Answer 19

It is further away, as the ultrasound has travelled further before being reflected

Question 20

What is the equation linking speed, distance and time?

Answer 20

Speed = Distance/Time

Question 21

What are disadvantages of X-rays?

Answer 21

-Ionising radiation (removal of electrons from atoms) could occur which may lead in some cases to mutations and cancers
-X-rays are not reflected at boundaries between different tissues, so are less good at scanning soft tissue and organs

Question 22

Why do we use ultrasound rather than X-rays for prenatal scanning?

Answer 22

-Ionising radiation is particularly dangerous to a developing foetus
-Any mutations could duplicate during growth and lead to more serious complications than in fully grown adults

Question 23

What are sound waves?

Answer 23

Sound waves are vibrations that travel through a medium

Question 24

Why can’t sound travel through a vacuum?

Answer 24

-Sound needs particles to travel
-A vacuum has no particles to vibrate, so sound can’t travel through it

Question 25

What is it called when a sound reflects off of a surface?

Answer 25

-An echo
-Echoes are better off flat surfaces

Question 26

What happens to the amplitude if the sound is quieter?

Answer 26

The amplitude is smaller

Question 27

What happens to the wavelength if the sound is higher pitch?

Answer 27

The wavelength decreases (waves are closer together)

Question 28

How do you hear sound?

Answer 28

-The ear can detect sound waves
-Sound waves make the ear drum vibrate
-They travel through the solid at this frequency
-Signals are sent to the brain
-The conversion to the solid has a limited frequency range
-For humans this is 20Hz to 20kHz

Question 29

Seismic waves are produced in an ______

Answer 29

earthquake

Question 30

Where does the earthquake spread out from?

Answer 30

The epicentre

Question 31

What is the epicentre?

Answer 31

-It is the nearest point on the surface to where the earthquake originates
-The actual origin is called the focus

Question 32

What are the 2 types of wave caused by earthquakes (and their types)?

Answer 32

-> P-waves (longitudinal)
-> S-waves (transverse)

Question 33

Where are P-waves capable of passing through?

Answer 33

Mantle and the outer core

Question 34

Where are S-waves capable of passing through?

Answer 34

The crust and the mantle, not the outer core

Question 35

What happens as the P-waves reach the boundaries between the mantle and the outer core?

Answer 35

-> P-waves refract due to different densities (change speed = change direction)