Waves

Question 1

What is meant by the amplitude of a wave?

Answer 1

It is the distance from the centre of the wave to the crest or trough

Question 2

What is meant by the frequency of a wave?

Answer 2

The number of waves generated or passing a point in 1 second

Question 3

What is meant by the wavelength of a wave?

Answer 3

It is the distance from a point on one wave to the same point on the next

Question 4

What is meant by the period of a wave?

Answer 4

The time it takes to generate one wave or for one wave to pass a point

Question 5

Describe how to measure the speed of sound with two students using a set of cymbals, stop watch and trundle wheel

Answer 5

• One student takes the cymbals and stands still
• The other students take the stop watch and use the trundle wheel to measure a set distance away
• The 1st student crashes the cymbals together once
• The other students start the stop watch when they see the cymbals crash together and stop it when they hear the sound
• Speed of sound is calculated by distance between the students divided by the time on the stop watch

Question 6

Describe how to measure the speed of sound using the equipment below

Answer 6

• Make a loud sound to the left of the 1st microphone
• When the sound reaches the microphone one, it starts the electronic timer
• When the sound reaches microphone two, the electronic timer stops
• Measure the distance between the 2 microphones using a metre stick
• The speed of sound is calculated by dividing the distance between the microphones by the time recorded buy the electronic timer

Question 7

You are 5km away from a thunder storm. What reaches you first - the thunder or the lightning? Explain your answer.

Answer 7

The lightning. The speed of light is faster than the speed of sound.

Question 8

You are 10km from a thunder storm. You count 15 seconds between seeing the lightning and hearing the thunder. How do you calculate how far away the storm is?

Answer 8

• Use d = vt
• where v is the speed of sound and t is 15 seconds
• The distance must be converted into meters

Question 9

You are 10km from a thunder storm. You count 15 seconds between seeing the lightning and hearing the thunder. You repeat this after the next lightning strike, the time between the lightning and thunder is now 10 seconds. What does this tell you?

Answer 9

The storm has moved closer to you.

Question 10

What is meant by a longitudinal wave?

Answer 10

A wave that vibrates along the direction of travel. In a longitudinal wave, the motion of the medium is parallel to the direction of the wave

Question 11

What is meant by a transverse wave?

Answer 11

A wave that vibrates at 90 degrees to the direction of travel. A transverse wave is a wave in which the motion of the medium is at right angles to the direction of the wave.

Question 12

What type of wave is a sound wave?

Answer 12

Longitudinal

Question 13

What type of wave is a water wave?

Answer 13

Transverse

Question 14

What type of wave is a microwave?

Answer 14

Transverse

Question 15

Name a longitudinal wave

Answer 15

Sound

Question 16

Name 3 transverse waves

Answer 16

• Radio
• Microwave
• Infrared
• Visible light
• Ultraviolet
• X-rays
• Gamma rays
• Water waves

Question 17

Name the members of the electromagnetic spectrum, from lowest to highest frequency

Answer 17

(Ronald Mcdonald Is Very Ugly eXclaimed George)

• Radio
• Microwave
• Infrared
• Visible light
• Ultraviolet
• X-rays
• Gamma radiation

Question 18

Which member of the electromagnetic spectrum has the most energy

Answer 18

Gamma radiation

Question 19

State one detector of radio waves

Answer 19

Aerial

Question 20

State one detector of microwaves

Answer 20

Aerial

Question 21

State one detector of infrared

Answer 21

• Photodiode
• Phototransistor

Question 22

State one detector of visible light

Answer 22

• Retina in the eye
• Photographic film

Question 23

State one detector of ultraviolet light

Answer 23

• Some chemicals glow or fluoresce under it
• Photocells

Question 24

State one detector of X-rays

Answer 24

Photographic film

Question 25

State one detector of gamma radiation

Answer 25

* Photographic film * GM tube * Bubble chamber

Question 26

State one source of radio waves

Answer 26

* Transmitter * Stars

Question 27

State one source of microwaves

Answer 27

* Transmitter * Magnetron

Question 28

State one source of infrared

Answer 28

* Stars * Lamps * Flames

Question 29

State one source of visible light

Answer 29

* The sun * Light bulbs * Fire

Question 30

State one source of ultraviolet light

Answer 30

* The sun * Special lamps

Question 31

State one source of X-rays

Answer 31

Stars

Question 32

State one source of gamma radiation

Answer 32

* Stars * Some radioactive substances (e.g. Cobalt 60)

Question 33

State one use of radio waves

Answer 33

* Radio/TV broadcasting * Aircraft and shipping bands * Radio waves detected from space are used by astronomers to find out what objects in space are made from

Question 34

State one use for microwave radiation

Answer 34

* Mobile phone communications * Used to heat/cook food * Microwaves in space are used by astronomers to learn about the structure of nearby galaxies, and our own Milky Way * Radar

Question 35

State one use for infrared radiation

Answer 35

* Skin emits infrared light so we can be seen in the dark by someone using night vision goggles * Astronomers use infrared to give information about space. Infrared light maps the dust between stars * Can be used to create thermograms which are used in medicine as a diagnostic tool for cancer, deep vein thrombosis (DVT), circulation problems * Remote controls for TVs, DVD, Bluray players, etc * Physiotherapists use heat lamps to help heal sports injuries

Question 36

State one use for visible light

Answer 36

* We use light to see! * Lasers are visible light and are used in Xbox, PlayStation, Bluray players, DVD players * Lasers are also used in laser printers * Aircraft weapon aiming systems

Question 37

State one use for ultraviolet radiation

Answer 37

* UV lamps in chip shops and butchers to attract insects * Detecting forged bank notes * Hardening some dental fillings * Night club lighting * UV security pens to mark property * Killing microbes - sterilising surgical equipment Food and drug companies use UV to sterilise products * Used by the body to produce vitamin D Used to treat skin disorders such as acne and psoriasis

Question 38

State one use for X-rays

Answer 38

* Create images of bone to detect breaks * Security to scan luggage at airports

Question 39

State one use for gamma radiation

Answer 39

* Used as a tracer in medicine * Used to treat cancer * Sterilisation of surgical instruments * Checking for cracks in metals e.g. aeroplane wings and joints

Question 40

How is the frequency of a wave related to its energy?

Answer 40

The higher the frequency, the more energy the wave has

Question 41

What is meant by the 'normal'?

Answer 41

An imaginary line drawn at 90 degrees to the surface. All angles are measured from the normal.

Question 42

What is meant by refraction?

Answer 42

Refraction is the **change of speed** of a wave as it enters a different medium. Often is is observed as a change in direction of the wave.

Question 43

What happens to the speed of light as it travels from air into glass?

Answer 43

It slows down

Question 44

Does a light ray always change direction when it is refracted?

Answer 44

No - if the angle of incidence is 0 degrees

Question 45

What do waves transfer?

Answer 45

Energy

Question 46

What is meant by diffraction?

Answer 46

It is the bending of waves round an object

Question 47

Will long or short wavelengths diffract more?

Answer 47

Long wavelengths diffract more

Question 48

In the hills why can you pick up a radio signal but not a television signal?

Answer 48

Radio waves are longer wavelengths than television waves. Radio waves diffract more and can reach the receiver.

Question 49

What is the difference in the diffraction pattern produced by waves passing through a wide and a narrow gap? (Wavelength is the same)

Answer 49

The narrower the gap, the more diffraction occurs.

Question 50

What is the difference in the diffraction pattern in a long wavelength and short wavelength passing an object?

Answer 50

The longer wavelength diffracts more

Question 51

What effect is shown here?

Answer 51

Diffraction

Question 52

Which wave priority is illustrated in the diagram below?

Answer 52

Amplitude

Question 53

Which wave property is illustrated below?

Answer 53

Wavelength

Question 54

In the diagram below, where is: * The normal? * The angle of incidence? * The angle of refraction?

Answer 54

See diagram

Question 55

What happens to a light ray as it travels from air into glass?

Answer 55

It will slow down and change direction towards the normal

Question 56

What happens to a light ray as it travels from water into air?

Answer 56

It speeds up and changes direction away from the normal

Question 57

What happens when white light is shone through a triangular prism as shown?

Answer 57

The light is refracted and produces a spectrum

Question 58

Which colour of light is refracted the most in a triangular prism when white light is shone through it?

Answer 58

Blue light

Question 59

Which colour of light is refracted the least in a triangular prism when white light is shone through it?

Answer 59

Red light

Question 60

Why does a triangular prism produce a spectrum from white light?

Answer 60

Different frequencies/colours of light are refracted by different amounts

Question 61

What is the difference between real and apparent depth? Explain how this happens.

Answer 61

We think that the water is shallower than it actually is (apparent depth) This is because * The light is refracted at the water/air boundary and changes direction away from the normal * Our eyes/brain assume that light travels in straight lines

Question 62

What is the shape of a convex lens?

Answer 62

See image

Question 63

What is the shape of a concave lens?

Answer 63

See image

Question 64

What effect does a convex lens have on parallel light rays?

Answer 64

The light rays converge to a focal point by refraction of the light

Question 65

What effect does a concave lens have on parallel light rays?

Answer 65

It causes them to diverge due to refraction of the light

Question 66

What is the difference in the 2 waves shown below?

Answer 66

The bottom wave has a higher frequency / or the top wave has a lower frequency

Question 67

What is the difference in the 2 waves shown below?

Answer 67

The top wave has a larger amplitude and so has more energy. (Or the bottom wave has a smaller amplitude so has less energy)

Question 68

What path will the ray of light take as it passes through the glass block?

Answer 68

Light ray still experiences a change of speed - it is still refracted but there is no change in direction

Question 69

What path will the ray of light take as it passes through the glass block?

Answer 69

The light ray is refracted at the air/glass boundary and glass/air boundary. Both result in a change in direction. As it enters the block, the speed of the light decreases and it changes direction towards the normal. As it leaves the block, the speed of the light increases and it changes direction away from the normal.