physics - waves Flashcards
1
Q
What do waves do?
A
Transfer energy from one area to another with out transferring matter
2
Q
What is the wavelength
A
The distance from one trough to another trough or peak to peak
3
Q
What is the amplitude
A
The amplitude of a wave is the maximum displacement
from the equilibrium position (the x-axis).
4
Q
What is the time period
A
The time period is the time it takes for one entire oscillation of the wave
5
Q
Unit for frequency
A
Hz
6
Q
What is a traverse wave
A
Oscillations are perpendicular to the direction of the energy transfer
7
Q
What is a longitudinal wave
A
Oscillations are parallel to the direction of the energy transfer
8
Q
Depending on conditions, when light hits a material it can be
A
Reflected, absorbed, transmitted
9
Q
Where does specular reflection happen
A
Specular reflection occurs on surfaces where the boundary is flat
10
Q
What type of image will specular reflection produce?
A
A clear image
11
Q
Where does diffuse reflection occur
A
Diffuse reflection occurs on materials where the surface is bumpy
12
Q
What is refraction
A
Refraction refers to changes in direction of the wave as it passes from one medium to another and it’s caused by it’s change in speed
13
Q
Light travels more ____ in a more dense material
A
slowly
14
Q
Light travelling from a less dense material to a more dense material will bend ____ the normal
A
towards
15
Q
Light travelling from a more dense material to a less dense material will _____ the normal
A
away from
16
Q
What happens to wave speed and frequency when a wave travels into a more dense medium
A
Wave speed - decreases
Frequency - Stays the same
17
Q
What happens to wave speed and wave length when a wave travels into a more dense medium
A
Wave speed - decreases
Wave length - decreases
18
Q
Are electromagnetic waves transverse of longitudinal
A
Transverse
19
Q
What speed does electromagnetic waves travel at in a vacuum
A
3 x 10(8) m/s
20
Q
What are true about radio waves
A
Have a long wavelength and low frequency
21
Q
What are true of gamma rays
A
Have a short wavelength and high frequency
22
Q
Which types of electromagnetic waves can be used in communication
A
Microwaves
Radio waves
23
Q
Which of the following types of electromagnetic waves are considered ionising?
A
Gamma rays
X rays
24
Q
How can you produce radio waves
A
Using an alternating current in an electrical circuit.
25
What are EM waves made up of
Electrical and magnetic fields
26
What are alternating currents made up of
Oscillating charges
27
How can you produce radio waves
Using an alternating current in an electrical circuit. The waves will be transmitted to the receiver and radio waves are absorbed.
28
What us a transmitter in terms of radio waves
The object in which charges oscillate to create the radio waves
29
What happens when the waves reach the receiver
The energy causes the electrons to oscillate and, if the receiver is part of a complete electrical circuit, it generates an alternating current. This current has the same frequency as the radio wave that generated it.
30
What are radio waves used for
Communication
31
How can long-wave radios be transmitted so far
They diffract around the curved surface of the Earth as well as hills and into tunnels. This makes it possible for radio signals to be receiver even if the receiver isn't in line of the sight of the transmitter.
32
How can short-wave radio signals be transmitted so far
They are reflected from the inonosphere
33
What wavelengths do TV and FM radio use
Very short wavelengths. To get reception, you must be in direct sight of the transmitter.
34
What wave on the EM spectrum has the longest wave length and the lowest frequency
Radio waves
35
What are oscilloscopes used for
To display the frequency of an alternating current
36
What EM wave is used by satellites and why
Microwaves can pass easily through the Earth's watery atmosphere
37
How does satellite TV work
The signal from a transmitter is transmitted into space where it's picked up by the satellite receiver dish orbiting thousands of kilometres above the earth. The satellite transmits the signal back to Earth in a different direction where it's received by a satellite dish on the ground.
38
What are microwaves used for
Microwave ovens and satellites
39
How do microwave ovens use microwaves
The microwaves are absorbed by water molecules in food. The microwaves penetrate up to a few centimetres into the food before being absorbed and transferring the energy they are carrying to thew water molecules in the food, causing the water to heat up. The water molecules then transfer this energy to the rest of the molecules in the food by heating - which quickly cooks the food
40
What are some uses of infrared radiation
Infrared cameras can be used to detect infrared radiation and monitor temperature.
Cooking food - the temperature of the food increases when it absorbs IR radiation
41
What are optical fibres
Thin glass or plastic fibres that can carry data over long distances as pulses of visible light
42
How do optical fibres work
The light rays are bounced back and forth ubtil they reach the end of the fibre
43
Uses of ultraviolet radiation
Passport security
Sun beds
Destroy microorganisms in water sterilisation.
44
What does fluorescense mean
property of a chemical where UV radiation is absorbed and then visible light is emitted
45
Uses of X-rays
X-rays are used to taker photographs of people to see if they have any broken bones
Can be used to treat people with caner
46
How do X-rays work
X-rays are able to pass through flesh easily but not so easily through denser material like bones or metal. So it's the amount of radiation that's absorbed that gives you an X-ray image.
47
Uses of gamma radiation
Used as a medical tracer
Can be used to treat cancer
48
How can gamma radiation and X-rays treat cancer
High doses of these rays kill all living cells - so they can be carefully directed towards cancer cells
49
How do lenses form images
By refracting light and changing its direction
50
Two main types of lenses
Concave and convex
51
Shape of convex lens and what does it cause rays to do
Bulges outwards and causes rays of light parallel to the axis to be brought together (converge) at the principal focus
52
Shape of concave lens and what does it cause rays to do
Caves inwards and causes rays of light to spread put (diverge) at the principal focus
53
What are the three things that objects do with wavelengths
Absorb, transmit and reflect
54
What are opaque objects
Objects that do not transmit light. When visible light waves hits them, they absorb some wavelengths of light and reflect others.
55
What does the colour of an opaque object depend on
Depends on which wavelengths of light are most strongly reflected. The other wavelengths are absorbed
56
What wavelengths do white objects reflect
White objects reflect all wavelengths of visible light equally.
57
What wavelengths do black objects reflect
Black objects reflect no light and absorb all wavelengths of visible light.
58
What do transparent and translucent objects do with light
They transmit light so not all light that hits the surface of the object is absorbed or reflected
59
What is a primary colour filter
Only allows one of the three primary colours to be transmitted
60
What are the primary colours
Red, green and blue
61
A green glass bottle appears green because:
The bottle reflects and/or transmits green light and absorbs other colours of light.
62
Objects that are hotter than their surroundings emit ____________ radiation than they absorb.
more
63
An object at room temperature emits mostly
infrared radiation
64
What happens to the land at night time
It absorbs more energy than it emits and its local temperature decreases
65
How does sound travel
As a wave
66
What are sound waves caused by
Caused by vibrating objects, these vibrations are passed through the surrounding medium as a series of compressions and rarefactions
67
How does sound travel in different states of matter
Sound generally travels faster in solids than in liquids
Faster in liquids than in gases
68
Why can't sound travel in space
Because it's mostly a vacuum so there are no particles to move or vibrate
69
What happens when sound waves reach your ear
Your eardrum can vibrate. These vibrations are passed on to tiny bones in your ear called ossicles, through the semicircular canals and to the cochlea.
70
What does the cochlea do
Turns these vibrations into electrical signals which get sent to your brain and allow you to sense (hear) the sound
71
What range of frequencies can humans here
20Hz - 20kHz
72
What limits human hearing
- The size and shape of our ear drum
- the structure of all parts within the ear that vibrate to transfer the energy from the sound wave.
73
When are sound waves reflected
Sound waves will be reflected by hard surfaces. Echoes are just reflected sound waves.
74
When are sound waves refracted
Sound waves will refract when they enter different mediums. As they enter denser material they speed up.
75
Why does the speed of a sound wave change when it enters a different medium
When a wave travels into a different medium, it's wavelength changes but it's frequency remains the same so its speed must also change.
76
What is ultrasound
A sound with frequency higher than 20,000Hz. It is an electrical device that produces electrical oscillations over a range of frequencies.
77
How do ultrasound waves work
Point a pulse of ultrasound at an object, and wherever there are boundaries between one substance and another, some of the ultrasound gets reflected back
78
What is ultrasound used in
Medical imaging eg. pre-natal scanning
Industrial imaging eg. finding flaws in materials
79
How is ultrasound used in medical imaging
- Ultrasound waves can be passed through the body, but whenever they reach a boundary between two different media (like fluid in the womb and skin of the foetus) some of the wave is reflected back and detected
The exact timings and distribution of these echoes are processed by a computer to produce a video image of a foetus
80
How is ultrasound used in industrial imaging
Ultrasound waves entering a material will usually be reflected by the far side of the material. If there is a flaw such as a crack inside the object the wave will be reflected sooner.
81
What is echo sounding
Uses high frequency sound waves to help boats and submarines find out the depth of the water that they are in, or to locate objects in deep water.
82
What thing scan happen when a wave reaches a boundary between materials
- the wave can completely reflect
- the wave can partially reflect
- the wave may continue travelling in the same direction but at a different speed
- the wave may be refracted
83
How are seismic waves produced
When there's an earthquake somewhere, it produces seismic waves which travel out through the Earth
84
How do we detect seismic waves
We detect seismic waves all over the surface of the planet, using seismometers
85
What happens to seismic waves when they reach a boundary
When seismic waves reach a boundary between different layers of material inside theEarth, some waves will be absorbed and some will be refracted.
86
What happens if seismic waves are refracted
They change speed gradally,resulting in a curved path
87
2 types of seismic waves
P-waves and S-waves
88
Differences between P waves and S waves
- P waves can travel through the Earth's core, but S-waves can't
- P waves are longitudinal ad S waves are transverse
- P waves can travel through solids and liquids but S-waves can't travel through liquids
- P -waves travel faster than S-waves
89
What is a perfect black body
An object that absorbs all of the radiation that hit it. No radiation is reflected or transmitted. They are alos the best possible emitters of radiation.
90
Relationship between temperature and intensity
As the temperature of an object increases, the intensity of every emitted wavelength increases.
91
How does wavelength effect intensity
The intensity increases more rapidly for shorter wavelengths than linger wavelengths. This causes the peak wavelength to decrease.
92
What does the overall temperature of the Earth depend on
The amount of radiation it reflects, absorbs and emits
93
what colour is the best at absorbing and emitting infrared radiation
A black surface is better at absorbing and emitting radiation than a white one, and a matte surface is better at absorbing and emitting radiation than a shiny one
94
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