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waves Flashcards

1
Q

Oscillate meaning of a wave

A

When a wave moves back and forth in repeating and regular way
(Another word for vibration)

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2
Q

Definition of transverse wave

A

Wave in which oscillations are perpendicular to the direction of energy transfer

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3
Q

Definition of longitudinal waves

A

Waves in which oscillations are parralel to direction of energy transfer

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4
Q

General definition of a wave

A

Transfers energy from one medium to the other without moving the medium in itself

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5
Q

Give five examples of transverse waves and two examples of a longitudinal wave

A

Transverse waves:
-light waves
-ripples on surface of water
-vibrations of guitar strings
- electromagnetic waves
- seismic S waves

Longitudinal waves
-sound waves
-seismic P waves

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6
Q

State why longitudinal waves can not move through a vacuum

A

Because they need particles to move

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7
Q

Definition of frequency

A

Number of complete waves in one second

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8
Q

Equation for wave speed

A

V (m/s) = f (hz)x lambda(m)

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9
Q

Give another way to express 1 hertz

A

1/T

Because F = 1/T

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10
Q

Time period meaning

A

Time taken for the number of complete waves to pass a point

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11
Q

Amplitude definition

A

The height of a wave, so distance between the rest point and the crest

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12
Q

Wavefront definition

A

Imaginary plane where vibrations are in phase and are the same distance from the source

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13
Q

Give two things that waves transfer

A

Energy and information

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14
Q

Give the structure of transverse waves, and the structure of longitudinal waves

A

Transverse waves= peaks and troughs
Longitudinal waves = rarefractiona and compressions

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15
Q

Give an example when the sound waves of a moving object are equally spaced:

A

When the object is moving at constant speed

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16
Q

When a wave source moves towards an observer, explain what they observe

A

Frequency is higher
Because wavefronts are more compressed
So wave length is shorter than original wave emitted
(And if sound, then pitch is higher)

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17
Q

Give the electromagnetic spectrum in order with up to three uses for each wave length

A

Radio waves—-) satellite communication AND radio + television
Microwaves—-)satellite communication AND cooking AND mobile phone calls
Infrared radiation—-) electric heating AND cooking AND temperature monitoring
Visible light—-)fibre optic communication AND photography
Ultraviolet——) fluorescent lamps AND sterilizes water
X-rays—-) medical imaging AND treatment
Gamma rays —-) sterilizing equipment + food AND destroying cancer cells

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18
Q

Comment on if these waves can move through a vaccum or not:
Longitudinal
Transverse

A

No longitudinal waves can travel through a vaccum
Only electromagnetic waves can travel through a vacuum for transverse waves

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19
Q

Explain the trend in properties of electromagnetic waves from radio waves to gamma rays(3)

A

Frequency increases
wave length becomes shorter
Energy transferred increases

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20
Q

What is special about electromagnetic waves and a vaccum

A

All travel at the same speed in a vacuum which is 3 x 10^8ms^-1

(And remember that they are the only transverse waves which can travel through a vacuum)

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21
Q

Which type of wave in electromagnetic spectrum has highest energy and which type of wave has lowest energy

A

Radio wave has lowest energy
Gamma ray has highest energy

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22
Q

Give four properties of all electromagnetic waves:

A

-all are transverse waves and are only transverse waves which can travel through a vaccum
-all travel at same speed through a vacuum which is 3 x 10^8ms
-transfer energy and not matter
-all can be reflected and refracted

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23
Q

Give the wave lengths of:
Radio waves
Visible light
Gamma rays

A

Radio waves: 1m-10^4m
Visible light: 10^-7m
Gamma rays: 10^-12m

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24
Q

How long are microwaves in centimeters

A

1cm

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25
An ambulance is stood still with its siren on, and two people are stood on either side of it same distance apart Explain the frequency that each person will hear
Both will hear same frequency because there are evenly spaced wave fronts And wave length distance is the same So will hear same pitch
26
Give a source of gamma rays
Radioactive material
27
Give a source of visible light
Luminous objects
28
Give a source and detector of a radio wave
Source = radio transmitter Detector= Aerial
29
Give a detector of visible light and a detector or infrared radiation
-the eye And then -a thermometer
30
Give a situation for radio waves in which shorter wave length radio waves are used: And longer wave length radio waves are used:
Shorter= Television and radio Longer= satellite communication
31
Explain why microwaves cook food faster than ovens do
-because the water molecules in the food can quickly absorb the microwaves -And so the heat energy can spread throughout in either conduction or convection(from centre to outside) -rather than only cooking the outside of the food
32
Explain why microwaves have metal reflectors inside them
To keep waves inside the microwave And prevent from reflecting outwards Because microwaves can heat human body tissue
33
Explain why microwaves emitted from mobile phones are less dangerous than those emitted from real microwaves
Because microwaves emitted from phones carry less energy And so can not harm human body tissue
34
Explain how waves are received from a satellite dish for satellite TV
-mircrowaves are released from transmitters -microwaves travel through space -satellite dish orbiting the earth picks up the signals
35
Which two electromagnetic waves sterilize equipment
Ultraviolet light and gamma rays
36
Give three uses of infrared radiation
Remote controls Thermo monitoring Cooking
37
Give two uses of radio waves
Broadcasting communication and radio/ television
38
Give three uses of microwaves
Satellite communication Mobile phones Cooking
39
Give two uses of visible light
Photography Fibre optic cables
40
Give three uses of ultraviolet light
Fluorescent lamps Sterilizes equipment Security marker pens
41
Give two uses of gamma rays
Sterilizes equipment Can destroy cancer cells
42
Explain why infrared radiation is good for remote controls
They only operate at small distances so will not interfere with other signals or waves
43
Information stored on CDs and barcodes can be detected by which kind of electromagnetic wave?
Visible light
44
Explain how fluorescent lamps emit visible light
When a current is passed, Mercury vapour gives off UV rays Which hit a coating on the tube, giving off white light
45
Describe how X-rays are able to be formed
Because X-rays are able to travel through body tissue, but not bones
46
Explain why it is important not to damage the ozone layer around the earth in terms of electromagnetic waves
Because the Ozone layer absorbs ultraviolet light, so without it skin cancer rates will increase
47
Give one way radiologist can protect themselves from X-rays and gamma rays
Can stand behind a lead screen
48
Give the dangers of all the electromagnetic waves
Radio waves—) N/A Microwaves—) can heat human body tissue Infrared radiation—) can create create skin burns Visible light-) N/A Ultraviolet—) harmful to eyes, increase skin cancer, cause burns and blisters X-rays—-) can cause cancer Gamma rays—-) can cause cancer and damage living things
49
Give two dangers of gamma rays
Can cause damage to living things and cause cancer because high levels of energy ionizes cells, thus mutating them
50
Explain why food stays fresher for longer after being exposed to gamma rays
Because gamma rays can kill microorganisms
51
State the relationship between luminous objects and light And non luminous objects and light
Luminous objects give out their own light (eg sun or light bulbs) Non luminous objects only reflect light
52
Explain why you can not see your reflection on a rough surface
Boundary is not flat so the normals will be pointing at different angles for each angle of incidence thus the angle of reflection will be emitted in different directions
53
What is the normal
An imaginary line that is perpendicular to the surface at point of incidence (where the wave hits the boundary)
54
Give two conditions for total internal reflection to occur
When angle of incidence is greater than the critical angle When light travels from more dense to less dense medium
55
What are the conditions for refraction to occur
When rays travel through different mediums, Cussing the speed to change, causing the direction to change
56
What are the conditions for reflection to occur
When light hits an even surface
57
Give the refractive index of glass and of water
Glass = 1.5 Water = 1.3
58
Give the refractive index equation
n= sin i/sin r
59
Give the equation for wave speed
V(m/s) = f(hz) x lambda (m) Or V= 1/T x lambda (Same things because another way to write frequency is 1/T
60
Explain what happens to light as it travels from less dense to more dense medium
Light slows down So wavelength decreases as long as frequency is the same And direction changes, bending closer to the normal And so angle of incidence is greater than angle of refraction
61
When light travels from less dense to more dense medium, state what happens to the direction in terms of from the Normal
Bends towards the normal
62
When light travels from more dense to less dense medium, state what happens to the direction in terms of from the Normal
Bends away from the normal
63
Explain what happens to light when it travels from a more dense medium to a less dense medium (In terms of speed, direction, the normal, wavelength)
Light rays speed up And direction changes, moving further away from the normal And wavelength So angle of incidence is smaller than angle of refraction
64
In an experiment to investigate the refraction, explain why your results may be inaccurate?
Because the width of the light ray you are using makes it difficult to locate where the centre of it is (Thus the crosses you make may not be accurate)
65
Explain why the angle of incidence and angle of reflection is the same for both Perspex and glass
Because the angle of incidence and angle of reflection is not affected by the medium
66
Explain how the angle of refraction going through glass and through Perspex will differ or be the same and why
Angle of refraction will be different for each Because angle of refraction is affected by the type of material
67
Give six steps to calculate the refractive index of a glass block
1)place a light box onto piece of paper with one slit in it, and direct the ray through the glass block so that it comes out on the opposite side 2)draw around the glass block and draw crosses over the light rays 3)remove the glass box and connect the light rays where the light entered the box and when it leaves the box 4)draw the normals 5) measure the angle of incidence and angle of refraction 6)use the equation n= sin i/sin r to calculate the refractive index
68
What is the critical angle
The smallest angle of incidence, at which light rays are totally internally reflected (Ur textbooks definition )
69
What is the critical angle of glass?
42 degrees
70
Explain how total internal reflection takes place in a prismatic prism
1) light enters at 90 so does not change direction. So light is undifferentiated 2)light passes through the next surface at 45 degrees and because critical angle of glass is 42 degrees, total internal reflection is able to happen 3)so light rays pass straight down to next prism and enters at 90 and does not change direction again 3) enters next surface at 45 degrees again so that total internal reflection can happen again so the ray leaves parallel to the original direction it was going in
71
Explain why optical fibers are better to use in telecommunication than copper wires
Have a thinner diameter so more fibers can be bunched together to carry more signals, so less energy is lost
72
Explain how optical fibers are used in telecommunication
Telephone sends electrical signals which are converted into light energy signals produced by a laser across bundles of optical fibers Which travel to a detector in the telephone receiver , changing the light signals into electrical signals
73
Give two examples of where optical fibers are used
Endoscopes or telecommunication
74
Give five examples of where total internal reflection is used
Endoscopes Telecommunication Periscope Binocular Bike reflectors
75
Explain how total internal reflection happens in binoculars
Light enters through lens into a prism Which refracts the light Then light is totally internally reflected into the next prism Then light is refracted again And then totally internally reflected again into the eye piece
76
Explain how total internal reflection occurs in endoscopes
Endoscopes have a low refractive index on the outside, and a high refractive index on the inside. It contains bunches of optical fibers, through which light from the light source enters And because it enters at an angle greater than the critical angle, it is able to totally internally reflect This light reaches the are of the Body And the light then travels back to the eye piece through another bunch of optical fibers through total internal reflection
77
Give a danger of visible light
If bright enough then can cause damage to eyes
78
Refractive index for diamond is 2.4 Refractive index for opal is 1.5 Which will be more sparkly? Explain why
Diamond Because it has a higher refractive index thus a smaller critical angle This means that there is a larger range of values for which total internal reflection can occur So if more total internal reflection, then it will sparkle more (Remember that the minimum angle that TIR can occur is the critical angle. So at any angle that is above the critical angle TIR will occur)
79
How do we hear?
Sound waves are longitudinal So when entering the ear they cause the ear drum to vibrate The vibrations are turned into electrical signals which we interpret
80
Describe an experiment to measure the speed of sound in air
1)You and your friend stand 100m apart from each other and measure this using a trundle wheel 2)Your friend will clap two pieces of wood together, 3)and you will start stop watch when you see them clap it, and will stop stopwatch when you hear the sound 4) repeat at least three times for a certain distance, then change distance and repeat 5)use the equation speed = distance / time and then calculate an average
81
Describe an experiment to calculate the speed of light in air
1)you and your friend should stand 100M away form each other and measure DISTANCE using a TRUNDLE WHEEL 2)friend will clap, and start timer when you see her bang two pieces of wood together and stop when you hear the sound 3)repeat three times for a certain distances and then repeat for different distances 4)use equation speed = distance/time and calculate an average
82
Explain why radio waves are used in broadcasting communication
Because they can be reflected from the earths surface
83
Explain why microwaves are used for satellite communication
Because they can penetrate the earths surface
84
Explain why visible light is used for fiber optic communication
Because it can undergo total internal reflection
85
Explain X-rays are used for medical imaging of bones
Because they can penetrate soft tissue but not bones
86
Explain why gamma rays are used for sterilzing medical equipment
Because they can kill bacteria
87
a student sitting on the shore of a lake watching ripples on the surface of the water moving past a toy boat. Explain how he can measure the frequency of the ripples
Count the number of waves that pass a point in a specific time, eg ten seconds Then use the equation F =number of waves/ time period
88
Give 2 properties of sound waves
All longitudinal waves Can not travel though a vaccum bc no particles
89
Which medium do sound waves travel fastest in and why
Because particles are closest together so vibrations will be fastest
90
Explain how tempeture can affect a sound wave
Temperature can increase or decrease the speed of the sound wave, therefore changing its direction (So it can be refracted)
91
Which types of waves can be refracted
All types (Both longitudinal and transverse)
92
When a wave slows down, what happens to its wave length and why
Wave length also decreases, Because wave speed and wave length are directly proportional (assuming frequency remains the same)
93
For a graph to show the relationship between critical angle and refractive index, give two reasons why the groah does not start at 0
1) a reduced scale, allow morw of the graph to fill the grid, thus showing the trend line more clearly 2)refractive index must always be larger than 1

physics (10 decks)

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