Waves Flashcards
(96 cards)
1
Q
Complete the sentence: Waves transfer __________ without transferring ____________.
A
energy, matter
2
Q
What is the amplitude of a wave?
A
The maximum displacement of a point on the wave from its undisturbed position.
3
Q
What is wavelength?
A
The distance between the same point on two adjacent waves.
4
Q
What is the frequency of a wave?
A
The number of complete waves passing a certain point per second. Measured in hertz.
5
Q
What is the period of a wave? State the equation.
A
The amount of time it takes for a full cycle of the wave to pass a point.
Period (s) = 1/ Frequency (Hz)
6
Q
What is a transverse wave?
A
A wave where the oscillations are perpendicular to the direction of energy transfer.
7
Q
What is a longitudinal wave?
A
A wave where the oscillations are parallel to the direction of energy transfer.
8
Q
What is the equation linking frequency, wave speed and wave length?
A
Wave speed (m/s) = Frequency (Hz) x Wave length (m)
9
Q
What piece of equipment can be used to measure the speed of sound?
A
Oscilloscope.
10
Q
Give a method for measuring the speed of sound.
A
- Set up the oscilloscope so the detected waves at each microphone are shown as separate waves.
- Start with both microphones next to the speaker, then slowly move one away until the two have aligned on the display, but have moved exactly one wave length apart.
- Measure the distance between the microphones to find one wavelength.
- Use the formula wave speed = frequency x wavelength to find the speed of the sound waves. The frequency is whatever you set the signal generator to.
11
Q
What piece of equipment can you use to measure the speed of water ripples?
A
A lamp.
12
Q
Give the method for measuring the speed of water ripples.
A
(Using a signal generator attached to the dipper of a ripple tank, you can create water waves at a set frequency)
- Dim the lights and turn on the lamp. A wave pattern can be seen made by the shadows of the water crests on the screen below the tank.
- The distance between each shadow line is equal to one wavelength. Measure the distance between shadow lines that are 10 wavelengths apart and then divide by 10 to find an average wave length.
- If you’re struggling take a photo of the shadows and ruler.
- Use Wave speed = frequency x wavelength to calculate the speed of the waves.
13
Q
Give the method for creating a wave on a string.
A
- Attach a signal generator to a vibration transducer. Attach a piece of string to the vibration transducer, a pulley and a weight.
- Adjust the frequency setting on the signal generator to change the length of the wave created on the string. Keep adjusting until a clear wave appears on the string.
- Measure the wavelength of the wave. To do this, measure the length of all the half-wavelengths on the string, then divide by the total number of half-wavelengths to get a mean. Then double to get a full wavelength.
- The frequency of the wave is what the signal generator is set to.
- To find the speed, use wave speed = frequency x wavelength.
14
Q
Complete the sentence: All waves can be a___________, t________ or r____________.
A
Absorbed, transmitted, reflected.
15
Q
What are the three things that can happen when a wave arrives at a boundary between two different materials?
A
- The waves are absorbed by the material - energy is transferred to the material’s energy store.
- The waves are transmitted - carry on travelling through the material (often refracted).
- The waves are reflected - bounce off in a different direction.
16
Q
What is the rule involving the angle of incidence and angle of reflection?
A
Angle of Incidence = Angle of Reflection
17
Q
What is the angle of incidence?
A
The angle between the incoming wave and the normal.
18
Q
What is the angle of reflection?
A
The angle between the reflected wave and the normal.
19
Q
What is the normal in a ray diagram?
A
An imaginary line that’s perpendicular to the surface at the point of incidence. Usually shown as a dotted line.
20
Q
What is the difference between specular reflection and diffuse reflection?
A
Specular reflection - happens when a wave is reflected in a single direction by a smooth surface.
Diffuse reflection - happens when waves are reflected by a rough surface and are scattered in lots of different directions (angle of incidence = angle of reflection still applies)
21
Q
What is refraction?
A
When light waves are bent when they enter a new media/material.
22
Q
What does the size of refraction depend on?
A
How much the wave speeds up or slows down (density).
23
Q
What direction does a wave bend when it crosses a boundary and slows down?
A
Towards the normal.
24
Q
What direction does a wave bend when it crosses a boundary and speeds up?
A
Away from the normal.
25
What happens to the frequency of a wave when it is refracted?
Stays the same.
26
When a wave is refracted in a material of high density does it slow down or speed up?
Slows down.
27
What is the optical density of a material?
A measure of how quickly light can travel through it. The higher the optical density, the slower light travels through it.
28
Explain how to construct a ray diagram to show refraction.
1. Draw the boundary between the two materials and the normal.
2. Draw an incident ray that meets the normal at the boundary.
3. Draw the refracted ray on the other side of the boundary. If the second material is optically denser than the first, the refracted ray bends towards the normal, so is smaller than the angle of incidence.
29
When doing light experiments, why does the room have to be dim?
So that you can clearly see paths of the rays of light.
30
Give the method for using transparent materials to investigate refraction.
1. Place a transparent rectangular block on a piece of paper and trace around it. Use a ray box or laser to shine a ray of light at the middle of one side of the block.
2. Trace the incident ray and mark where the light ray emerges on the other side of the block. Remove the block and draw a straight line to join up the incident ray and the emerging point to show the path of the refracted ray through the block.
3. Draw the normal at the point where the light ray entered the block. Use a protractor to measure the angle between the incident ray and the normal and then the angle between the refracted ray and the normal.
4. Repeat this experiment using rectangular blocks made from different materials, keeping the incident angle the same throughout.
31
How could you make the required practical investigating refraction through different transparent materials more accurate?
- Use a laser instead of ray box to produce thin rays of light.
32
Complete the sentence: How light reflects depends on the _____________ of the surface.
smoothness
33
Give a method for investigating how different surfaces reflect light.
1. Take a piece of paper and draw a straight line across it. Place an object so one of its sides lines up with this line.
2. Shine a ray of light at the objects surface and trace the incoming and reflected light beams.
3. Draw the normal at the point where the ray hits the object. Use a protractor to measure the angle of incidence and the angle of reflection and record these values in a table. Make a note of the width and brightness of the reflected light ray.
4. Repeat this experiment for a range of objects.
34
What type of waves are electromagnetic waves?
Transverse.
35
What are electromagnetic waves?
Transverse waves that transfer energy from a source to an absorber. They are vibrations of electric and magnetic fields.
36
Can electromagnetic waves travel through a vacuum?
Yes.
37
Give the order of electromagnetic waves with increasing frequency and decreasing wave length.
Radio waves
Micro waves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays
38
Which electromagnetic wave has the highest frequency?
Gamma rays.
39
Which electromagnetic wave has the highest wavelength?
Radio waves.
40
Complete the sentence: All EM waves travel at the s_______ s______ through air or a vacuum.
same speed.
41
What are radio waves made up of?
Oscillating charges (electric and magnetic).
42
What type of current is made up of oscillating charges?
Alternating current.
43
What are radio waves used for? Why?
Communication. The long wavelengths diffract around the curved surface of the Earth and can be received at long distances from the transmitter. Short-wave radio signals reflect off the ionosphere.
44
What are the wavelengths of the 7 electromagnetic waves?
Radio waves -> 1m - 10^4m
Microwaves -> 10^-2m
Infrared ->. 10^-5m
Visible light -> 10^-7m
Ultraviolet -> 10^-8m
X-rays -> 10^-10m
Gamma rays -> 10^-15m
45
What type of EM wave is used by satellites?
Microwaves
46
Why are microwaves used by satellites?
They can pass through the atmosphere.
47
Explain how microwaves are used by satellites.
- The signal from a transmitter is transmitted to space.
- The satellite receiver dish orbiting the earth picks up the signal and then transmits it back to earth in a different direction.
- It is then received by a satellite dish on the ground. There is a slight delay due to the large distance.
48
Explain how microwave ovens work.
The microwaves are absorbed by water molecules in food. They penetrate up to a few centimetres into the food before being absorbed and transferring the energy they are carrying to the water molecules in the food, making it 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.
49
What is infrared radiation used for?
To monitor temperature or increase it.
50
How does infrared radiation show the temperature of an object?
The hotter an object, the more infrared radiation it gives out.
51
What piece of equipment can be used to detect infrared radiation and monitor temperature? How does it work?
Infrared cameras. It detects the radiation and turns it into an electrical signal which is displayed on a screen as a picture. The hotter an object is, the brighter it appears.
52
How does infrared radiation cook food?
Absorbing IR radiation causes objects to get hotter. The temperature of the food increases when it absorbs IR radiation.
53
Give an example of an appliance that uses infrared radiation to cook food.
A toaster or electric heater.
54
How do electric heaters work?
They contain a long piece of wire that heats up when a current flows through it. This wire emits lots of IR radiation. The radiation is absorbed by objects and the air in the room causing the temperature to increase.
55
What are optical fibres?
Thin glass or plastic fibres that can carry data over long distances as pulses of visible light.
56
How do fibre optic cables transmit data?
Through pulses of visible light. They work due to reflection, the light rays are bounced back and forth until they reach the end of the fibre.
57
What is fluorescence?
A property of certain chemicals, where ultraviolet radiation is absorbed and then visible light is transmitted.
58
What emits ultraviolet radiation?
The sun.
59
What are the uses of ultraviolet radiation?
- Fluorescent lights
- Security pens
- Tanning Salons
60
Why do X-rays and gamma rays have similar properties?
They are both at the short wavelength end of the electromagnetic spectrum.
They carry much more energy per second than longer wave length EM waves.
61
How are X-rays and gamma rays different?
X-rays are produced when electrons or other particles moving at high speeds are stopped.
Gamma rays are produced by radioactive substances when unstable nuclei release energy.
Gamma rays have shorter wavelengths so are more penetrating.
62
What are the uses of gamma rays?
Killing harmful bacteria - food and surgical equipment.
Killing cancer cells.
63
What are the uses of X-rays?
To make images of your internal body parts.
To destroy tumours at or near the body surface.
64
How are X-rays used in medicine?
When the X-ray tube is turned on, X-rays from the tube pass through the the part of the patient’s body under investigation.
X-rays pass through soft tissue, but are absorbed by bones, teeth and metal objects that are not too thin.
The parts that absorb the X-rays appear lighter than the surrounding tissue that appears dark.
65
How can X-rays be used to look at organs made up of soft tissue?
It can be filled with a substance called a contrast medium that absorbs X-rays easily. This allows it to be seen on the radiograph.
66
How do radiographs/ X-ray photographs work?
A flat panel detector is a small screen that contains a charge-coupled device (CCD). The sensors in the CCD convert the X-rays into light. The light rays then create electronic signals in the sensors that are sent to a computer, which displays a digital X-ray image.
67
What do radiographers do to protect themselves from X-rays and gamma rays?
Wear lead aprons, stand behind a lead screen or leave the room.
68
What is radiation dose?
A measure of the damage done to a person’s body by ionising radiation.
69
What does the radiation dose depend on?
- The type of radiation used
- How long the body is exposed to the radiation
- The energy per second absorbed by the body from the radiation
70
What is X-ray therapy used for?
Destroying cancerous cells in the body.
71
What are the three rules for refraction in a convex lens?
1. An incident ray parallel to the axis refracts through the lens and passes through the principle focus on the other side.
2. An incident ray passing through the principle focus reflects through the lens and travels parallel to the axis.
3. An incident ray passing through the centre of the lens carries on in the same direction.
72
What are the three rules of refraction in a concave lens?
1. An incident ray parallel to the axis refracts through the lens and travels in line with the principle focus.
2. An incident ray passing through the lens towards the principle focus refracts through the lens and travels parallel to the axis.
3. An incident ray passing through the centre of the lens carries on in the same direction.
73
Draw a ray diagram for a convex lens.
- Oval shaped lens
- Principle focus in front of the convex lens
- Light rays travel and meet at the principle focus
74
Draw a ray diagram for a concave lens.
- Not an oval shaped lens
- principle focus is behind lens
75
What is a real image?
Where the light from an object comes together to form an image on a screen.
76
What is a virtual image?
When the rays are diverging, so the light from the object appears to be coming from a completely different place.
77
What 3 things do you need to say when describing an image?
- How big it is compared to the object (enlarged or diminished)
- Whether it is upright or inverted
- Whether it is real or virtual
78
Explain how to draw a ray diagram for an image through a convex lens.
1. Pick a point on the top of the object. Draw a ray going from the object to the lens parallel to the axis of the lens.
2. Draw another ray from the top of the object going through the middle of the lens.
3. The incident ray thats parallel to the axis is refracted through the principle focus on the other side of the lens. Draw a refracted ray passing through the principle focus.
4. The ray passing through the middle of the lens doesn’t bend.
5. Mark where the rays meet. That’s the top of the image.
6. Repeat the process for a point on the bottom of the object. If the bottom of the object is on the axis then the bottom of the image is also on the axis.
79
Explain how to draw a ray diagram for an image through a concave lens.
1. Pick a point on the top of the object. Draw a ray going from the object to the lens parallel to the axis of the lens.
2. Draw another ray from the top of the object going right through the middle of the lens.
3. The incident ray thats parallel to the axis is refracted so it appears to have come from the principle focus. Draw a ray from the principle focus. Make it dotted before it reaches the lens.
4. The ray passing through the middle of the lens doesn’t bend.
5. Mark where the refracted rays meet. That’s the top of the image.
6. Repeat the process for a bottom point. When the bottom of the object is on the axis, the bottom of the image is also on the axis.
80
Complete the sentence: A concave lens ____________ produces a virtual image.
always.
81
What colours make up white light?
All.
82
Name the order of colours.
Red
Orange
Yellow
Green
Blue
Indigo
Violet
83
What colours of light does a blue object absorb?
All but blue.
84
What colour does a red hat appear through a blue filter?
Black.
85
What is a perfect black body?
An object that absorbs all of the radiation that hits it. No radiation is reflected or transmitted.
86
What is ultrasound?
Sound with frequencies higher than 20,000 Hz.
87
Complete the sentence: Ultrasound waves get __________ reflected at boundaries.
Partially.
88
What are ultrasounds used for in the medical industry?
Ultrasounds can pass through the body but when they reach a boundary between two different media, some of the wave is reflected back and detected. This is used to create images of babies in the womb as there is fluid in the womb and the skin of the foetus. Ultrasound is less dangerous than X-rays.
89
What are seismic waves?
Body waves which travel through the earth.
90
What causes seismic waves?
Earthquakes and explosions.
91
What is used to detect seismic waves?
Seismometers.
92
What happens when seismic waves reach a boundary between different layers of material?
Some waves are absorbed and some are refracted.
93
What happens when seismic waves are refracted at a boundary?
They gradually change speed, resulting in a curved path.
94
What are the two different types of seismic waves?
P waves and S waves.
95
What are P waves?
They are longitudinal waves that can travel through the earth’s core. They can travel through solids and liquids and are faster than S waves.
96
What are S waves?
They are transverse waves that cannot travel through liquids or gases, so cannot travel through the earth’s core. They are slower than P waves.
