Unit 3 - Waves

Question 1

Transverse waves…?

Answer 1

Are waves that oscillate perpendicular to the direction of energy transfer.
↳ The energy transfer is perpendicular to wave motion

They can move in solids surface of liquids and vacuums (they don’t require a medium to travel) but not in liquids and gases.

Question 2

Longitudinal waves..?

Answer 2

Are waves where the points along its length vibrate parallel to the direction of energy transfer.
↳ The energy transfer is in the same direction as the wave motion

They can move in solids, liquids and gases, but they can not move in a vacuum (since there are no particles)

Question 3

What is the SI unit of frequency?

Answer 3

Hertz (Hz)

Question 4

What is the SI unit of length?

Answer 4

Metres (m)

Question 5

What is the SI unit of speed and velocity?

Answer 5

Metres per second (m/s)

Question 6

What is the SI unit of time?

Answer 6

Seconds (s)

Question 7

What unit is used when measuring angles?

Answer 7

Degrees

Question 8

What is the definition of amplitude?

Answer 8

The maximum displacement of a wave from its rest (equilibrium) position.

Question 9

What is the definition of wavefront?

Answer 9

It is an imaginary surface representing corresponding points of a wave that vibrate in unison.

Question 10

What is the definition of frequency?

Answer 10

The number of waves that pass a given point in one second.

Question 11

What is a period of a wave?

Answer 11

The amount of time it takes for a wave to complete one cycle.

Question 12

What is the definition of wavelength?

Answer 12

It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests or troughs.

Question 13

What do waves transfer?

Answer 13

Waves transfer energy not matter.

Question 14

What is an equation of a wavelength?

Answer 14

wave speed = frequency × wavelength
v = f × λ

Question 15

What is an equation of frequency?

Answer 15

frequency = 1/ time period
f = 1/T

Question 16

What is the doppler effect?

Answer 16

The apparent change in wavelength and frequency of a wave emitted by a moving source. This frequency change due to the relative motion between a source of sound or light and an observer.

Question 17

What happens to frequency with movement?

Answer 17

• The frequency is increased when the source is moving towards the observer
• The frequency is decreased when the source is moving away from the observer

Question 18

What waves can be reflected and refracted?

Answer 18

Both waves, longitudinal and transverse can be reflected and refracted.

Question 19

The electromagnetic spectrum (lowest → highest frequency)

Answer 19

Radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays

Question 20

The colours of the visible spectrum (decreasing in wavelength)

Answer 20

Red, orange, yellow, green, blue, indigo, violet

• Red has the longest wavelength (and the lowest frequency and energy)
• Violet has the shortest wavelength (and the highest frequency and energy)

Question 21

Trends in the electromagnetic spectrum (radio waves…gamma rays)

Answer 21

• The energy increases
• The wavelength decreases
• The frequency increases

Question 22

Applications for radio waves

Answer 22

Broadcasting and communication (radio and TV)

Question 23

Applications for microwaves

Answer 23

Cooking and communication (WiFi, mobile phones and satellites)

Question 24

Applications for infrared

Answer 24

Heaters and night vision equipment

Question 25

Applications for visible light

Answer 25

Optical fibres and photography

Question 26

Applications for ultraviolet

Answer 26

Fluorescent lamps

Question 27

Applications for x-rays

Answer 27

Observing the internal structure of objects and materials, including for medical applications

Question 28

Applications for gamma rays

Answer 28

Sterilising food and medical equipment

Question 29

Effects of excessive exposure to microwaves

Answer 29

Internal heating of body tissue

Question 30

Effects of excessive exposure to infrared

Answer 30

Skin burns

Question 31

Effects of excessive exposure to ultraviolet

Answer 31

Damage to surface cells and blindness

Question 32

Effects of excessive exposure to gamma rays

Answer 32

Cancer, mutation

Question 33

What is the law of reflection?

Answer 33

The angle of incidence equals the angle of reflection.

Question 34

Refractive index formula

Answer 34

refractive index = sin i/ sin r
n = sin i/ sin r

Question 35

Whats the hearing range for humans?

Answer 35

20 - 20000 Hz