Waves Flashcards
1
Q
What do waves transfer from one place to another?
A
Energy
Waves do not transfer matter.
2
Q
In which direction do waves transfer energy?
A
In the direction they are travelling.
3
Q
What happens to particles of a medium when waves travel through it?
A
Particles oscillate and transfer energy between each other.
4
Q
What is the amplitude of a wave?
A
The maximum displacement of a point on the wave from its undisturbed position.
5
Q
Define wavelength.
A
The distance between the same point on two adjacent waves.
6
Q
How is frequency measured?
A
In hertz (Hz).
7
Q
What is the formula to find the period of a wave?
A
T = 1/f.
8
Q
What are the two main types of waves?
A
Transverse and longitudinal waves.
9
Q
Describe the oscillations in transverse waves.
A
They are perpendicular to the direction of energy transfer.
10
Q
Give an example of transverse waves.
A
- All electromagnetic waves (e.g., light)
- Ripples and waves in water
- Waves on a string.
11
Q
What characterizes longitudinal waves?
A
The oscillations are parallel to the direction of energy transfer.
12
Q
Provide an example of longitudinal waves.
A
Sound waves in air.
13
Q
What is the wave speed formula?
A
Wave speed = Frequency × Wavelength.
14
Q
What does the wave equation apply to?
A
All waves.
15
Q
If a radio wave has a frequency of 12.0 × 10^6 Hz, what is its wavelength if the speed is 3.0 × 10^8 m/s?
A
25 m.
16
Q
What equipment is used to measure the speed of sound?
A
An oscilloscope and microphones.
17
Q
What is the typical speed of sound in air?
A
Around 330 m/s.
18
Q
How can you measure the speed of water ripples?
A
Using a ripple tank with a signal generator.
19
Q
What should you do to find the average wavelength in a ripple tank experiment?
A
Measure the distance between shadow lines that are 10 wavelengths apart and divide by 10.
20
Q
What is the purpose of using a vibration transducer in wave experiments on strings?
A
To make the string vibrate.
21
Q
How can you accurately measure the wavelength of waves on a string?
A
Measure the lengths of several half-wavelengths and divide to find the mean half-wavelength.
22
Q
What is the relationship between frequency and wavelength in a wave equation?
A
Frequency (f) is inversely related to wavelength (λ) in the equation v = fλ.
23
Q
What are the three possible outcomes when a wave meets a boundary between two materials?
A
- The wave is ABSORBED
- The wave is TRANSMITTED
- The wave is REFLECTED
Each outcome depends on the properties of the materials and the wavelength of the wave.
24
Q
What happens when a wave is ABSORBED by a material?
A
The wave transfers energy to the material’s energy stores, often leading to heating.
This is how a microwave oven functions.
25
What does it mean for a wave to be TRANSMITTED through a material?
The wave continues to travel through the new material, often leading to refraction.
26
What is REFLECTION in the context of wave behavior?
The incoming ray is sent back away from the second material without being absorbed or transmitted.
27
What type of waves are electromagnetic (EM) waves?
Transverse waves.
28
Do all EM waves travel at the same speed in a vacuum?
Yes, all EM waves travel at the same speed through air or a vacuum.
29
What is the range of wavelengths for electromagnetic waves?
From around 10^-15 m to more than 10^4 m.
30
What is the mnemonic to remember the order of electromagnetic waves?
'Rock Music Is Very Useful for eXperiments with Goats'.
31
What causes different types of electromagnetic waves?
Variety of changes in atoms and their nuclei.
32
What is the optical density of a material?
A measure of how quickly light can travel through it.
33
What happens to the wavelength of a wave when it is refracted?
The wavelength changes, but the frequency stays the same.
34
True or False: A wave changes direction when it crosses a boundary at an angle.
True.
35
What is the angle of incidence?
The angle between the incident ray and the normal.
36
How does a wave behave when it enters a denser material?
The refracted ray bends towards the normal.
37
How can you illustrate the path of a wave using ray diagrams?
By drawing straight lines that are perpendicular to wave fronts.
38
What is a wave front?
A line showing all points on a wave that are in the same position after a given number of wavelengths.
39
What happens to a wave front when it crosses a boundary at an angle?
Only part of the wave front crosses the boundary at first, causing it to bend.
40
Fill in the blank: The part of a wave front traveling into a denser material travels ______ than the rest of the wave front.
slower.
41
What type of waves are primarily used for communication?
Radio waves
## Footnote
Radio waves are electromagnetic radiation with wavelengths longer than about 10 cm.
42
How are radio waves produced?
By oscillating charges in an electrical circuit
## Footnote
The object in which charges oscillate to create radio waves is called a transmitter.
43
What is the relationship between the frequency of alternating current and the frequency of produced radio waves?
They are equal
## Footnote
The frequency of the waves produced will be equal to the frequency of the alternating current.
44
What happens when radio waves reach a receiver?
They are absorbed by the receiver
## Footnote
This absorption causes electrons in the receiver to oscillate.
45
What is the role of electrons in the receiver when radio waves are absorbed?
They oscillate and generate an alternating current
## Footnote
If the receiver is part of a complete electrical circuit, it generates an alternating current with the same frequency as the radio wave.
46
What are the characteristics of long-wave radio?
Wavelengths of 1 - 10 km
## Footnote
Long-wave radio can diffract around obstacles and be received at long distances.
47
What allows long-wave radio signals to be received even without line of sight to the transmitter?
Diffraction around hills and obstacles
## Footnote
This property makes long-wave signals versatile in reception.
48
What is the wavelength range for short-wave radio signals?
About 10 m - 100 m
## Footnote
Short-wave signals can be received at long distances due to reflection from the ionosphere.
49
What technology uses short-wave radio waves for communication?
Bluetooth®
## Footnote
Bluetooth® allows wireless data transmission over short distances.
50
What is required for FM and TV signals to be received?
Direct line of sight to the transmitter
## Footnote
FM and TV signals have very short wavelengths and do not bend around obstacles.
51
What type of waves are used by satellites for communication?
Microwaves
## Footnote
Microwaves can pass easily through the Earth's watery atmosphere.
52
How do microwave ovens use microwaves?
Microwaves are absorbed by water molecules in food
## Footnote
This absorption causes the water to heat up and cook the food.
53
What is infrared radiation (IR) emitted by?
All objects
## Footnote
The hotter the object, the more IR radiation it emits.
54
How do infrared cameras work?
They detect IR radiation and display it as a picture
## Footnote
The intensity of the detected IR radiation is shown with different colors, indicating temperature.
55
What happens when objects absorb infrared radiation?
Their temperature increases
## Footnote
This is because absorbing IR radiation transfers energy to the object's thermal energy store.
56
How do electric heaters emit infrared radiation?
By heating a wire when current flows through it
## Footnote
The heated wire emits IR radiation which is absorbed by objects and air in the room.
57
Fill in the blank: Radio waves are EM radiation with wavelengths longer than about ______.
10 cm
58
True or False: Short-wave radio signals can be received at long distances due to diffraction.
False
## Footnote
Short-wave signals are reflected from the ionosphere, not diffracted.
59
What is the effect of microwaves in food when used in microwave ovens?
They cause water molecules to heat up
## Footnote
This heat is then transferred to the rest of the food, cooking it.
60
What are optical fibres?
Thin glass or plastic fibres that can carry data over long distances as pulses of visible light
## Footnote
They work through the principle of reflection.
61
Why is visible light used in optical fibres?
Because it is easy to refract light enough so that it remains in a narrow fibre
## Footnote
Light is also not easily absorbed or scattered as it travels along a fibre.
62
What is fluorescence?
A property of certain chemicals where ultra-violet (UV) radiation is absorbed and then visible light is emitted.
63
How do fluorescent lights work?
They generate UV radiation, which is absorbed and re-emitted as visible light by a layer of a compound called phosphor inside the bulb.
64
What are security pens used for?
To mark property with your name, which glows under UV light but is invisible otherwise.
65
What is the effect of ultraviolet radiation (UV) from the Sun?
It gives people a suntan.
66
What are X-rays used for in hospitals?
To take 'photographs' of people to see if they have any broken bones.
67
Why do X-rays pass easily through flesh but not through bones or metal?
Because the amount of radiation absorbed differs between materials.
68
What is radiotherapy?
A treatment that uses X-rays and gamma rays to kill cancer cells.
69
What is a medical tracer?
A gamma-emitting source injected into a patient to follow its progress around the body.
70
What precautions do radiographers take when using X-rays and gamma rays?
They wear lead aprons and stand behind lead screens or leave the room.
71
What does a Leslie cube investigate?
The amount of infrared radiation emitted from an object based on its surface material.
72
What surfaces are typically tested in a Leslie cube experiment?
Matt black paint, matt white paint, shiny metal, and dull metal.
73
What is the melting wax trick used to demonstrate?
The amount of infrared radiation absorbed by different materials.
74
In the melting wax experiment, which surface absorbs more infrared radiation?
The matt black surface absorbs more than the silver surface.
75
Fill in the blank: The ball bearing on the black plate will fall first because the black surface absorbs more _______.
infrared radiation.
76
True or False: Fluorescent colours look bright because they emit light.
True.
77
Why is it important to repeat the Leslie cube experiment?
To ensure the results are repeatable.
78
What happens to a black mug compared to a white mug when cooling tea?
The black mug cools at a faster rate.
79
What can some electromagnetic radiation be harmful to?
People
## Footnote
Electromagnetic radiation can have both useful and harmful effects.
80
How do low frequency waves like radio waves interact with soft tissue?
They mostly pass through without being absorbed
## Footnote
Low frequency waves transfer little energy.
81
What types of high frequency waves can cause damage?
UV, X-rays, and gamma rays
## Footnote
High frequency waves transfer a lot of energy.
82
What is one effect of UV radiation on the skin?
Causes sunburn
## Footnote
Other effects include premature aging and increased risk of skin cancer.
83
What can X-rays and gamma rays cause at the cellular level?
Gene mutation or cell destruction
## Footnote
This can potentially lead to cancer.
84
What is radiation dose measured in?
Sieverts
## Footnote
This measure indicates the risk of harm from radiation exposure.
85
What determines the risk of harm from radiation?
Total amount of radiation absorbed and the harmfulness of the radiation type
## Footnote
Different types of radiation have different risk levels.
86
How is a sievert often expressed in smaller units?
Millisieverts (mSv)
## Footnote
1000 mSv = 1 Sv.
87
In a CT scan, which body part has a higher risk of genetic damage?
Chest
## Footnote
The risk is four times higher for a chest scan compared to a head scan.
88
What is the radiation dose for a CT scan of the chest?
8.0 mSv
## Footnote
The dose for a head scan is 2.0 mSv.
89
What is the radiation dose for an X-ray of the pelvis?
0.7 mSv
## Footnote
This is compared to 7 mSv for a CT scan of the pelvis.
90
How much larger is the added risk of harm with a CT scan of the pelvis compared to an X-ray?
Ten times larger
## Footnote
The CT scan dose is 7 mSv versus 0.7 mSv for the X-ray.
91
True or False: It is possible to avoid all forms of harmful radiation.
False
## Footnote
It's about balancing risks and reducing exposure.
92
Give two effects of a person being exposed to too much UV radiation.
1. Sunburn
2. Increased risk of skin cancer
## Footnote
Additional effects can include premature skin aging.
