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Physics Year 11 > Waves > Flashcards

Waves Flashcards

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1
Q

What are waves

A

Means of transferring energy from place to place or information

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2
Q

Transverse waves

A

Vibrate at right angles to the direction in which the wave or energy is moving e.g light

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3
Q

Longitudinal waves

A

Vibrations along the direction the wave or energy is moving in

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4
Q

What is amplitude

A

The heights point on the wave from resting point (height from 0)

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5
Q

What is the wavelength

A

Distance from crest to crest

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6
Q

What is frequency

A

The number of waves produces each second measured in Hz

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7
Q

Equation for frequency

A

Time period ( time in seconds in seconds needed for a source to produce one wave )

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8
Q

What is the wave equation got wave sped

A

Wave Speed (m/s) = frequency (Hz) x wavelength (metres )

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9
Q

When are waves reflected

A

When a wave strikes a straight or flat barrier , the angle of incidence (the angle the she struck the barrier) is equal to the angle of reflection

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10
Q

What hapoens if a wave strikes a concave barrier

A

They are reflected backwards and converge

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11
Q

What happens when a wave strikes a convex barrier

A

They are reflected backwards and diverge ( spread out )

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12
Q

What happens in refraction e.g. Putting a glass plate in the ripple tank

A

Depth of water is reduced so when the waves enter this region their wave length becomes shorter but their frequency is unaltered so they are traveling more slowly but when they enter the deeper water again their speed increases . If the boundary between shallow and deep water is at an angle to the direction the waves are moving the waves are refracted and bebd towards normal as they enter the shallow water and are slowed down , then they bend away from the normal as they leave the shallow water and eneter the deeper water

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13
Q

When can refraction happen

A

If the boundary between shallow and deep water is at an angle to the direction which the waves are moving the direction of the wave changes

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14
Q

What happens in diffraction

A

If size of gap is about equal to wavelength of waves the waves are diffracted and spread out from Their straight on direction . This is called diffraction e.g sound waves moving through doorways . If gap is larger than wave length waves just continue In same direction , some are diffracted

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15
Q

What properties do the elctromagnetic spectrum have

A

They all transfer energy
They are all transverse waves
They all travel at the speed of light in a vacuum
They can all be reflected refracted and diffracted

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16
Q

How do the EM waves differ

A

One end of spectrum - long wave length low frequency

Other end of spectrum - high frequency short wave length

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17
Q

Radio waves

A

Lowest frequency , longest wavelength , sources of radio transmitters , tv transmitters , detected by radio and tv aerials and used for radio and tv picks up radio waves and converts it into mechanical vibrations in the speaker to create sound waves that can be heard

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18
Q

Microwaves

A

2nd on spectrum
Oven -electric circuit produces microwave guides to food by rotating reflector which sends microwaves in all direction the microwaves are absorbed by food and become hot
Communications - pass easily through earths atmosphere so they carry signals to orbiting satellites which then pass signals alone, mobile phones use microwaves to carry messages
Hazards - heating body tissue
Higher frequency more damage it caused

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19
Q

Infrared

A

3rd on spectrum given out by hot objects and is used for thermal imaging cameras and cooking e.g. Could in a toaster tv and remote controls send infra red pulses which the device recognises
This is good because the waves have a low penetrating power so only operate over small distances and are unlikely to interfere with other signals or waves.Hazards are burns

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20
Q

Visible light

A

4th on spectrum given out by luminous objects , and detected by the eye , photographic film
Is used in seeing optical fibres and photography or reading barcodes
Hazards are light burning holes in your retina and concentrated light rays can damage skin

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21
Q

UV

A

5th on spectrum emitted by sun and uv lamps and can be detected by skin photographic film and some fluorescent chemicals is used for uv tanning lamps and fluorescent tubes
Hazards - damage to surface cells such as skin cancer , sunburn and blistering , blindness

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22
Q

X-rays

A 
6th on spectrum pass easily through body tissue but can't pass through bones so leave a paler image f bones on an X-ray image as they allow less X-rays through 
Source - X-ray tube 
Dectecor - photographic films
Hazards can cause cancer 
Very penetrating
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23
Q

Gamma rays

A

7th highest frequency shortest wavelength most harmful as very penetrating
Sources - radioactive material
Dectector - Geiger muller tube
Uses - sterilising equipment and food radiotherapy
Hazards - kills cells causes mutation

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24
Q

How are microwaves used to find the position of an aeroplane in the sky

A

Rotating aerial transmits pulses of microwaves which are reflected off aeroplanes this is then detected by the aerial and the time delay is used to calculate the distance of the aeroplane

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25
How do digital signals work
To communicate information over a long distance of must be converted into electrical signals (either digital or analogue ) before it's transmitted down either telephone wires or on EM waves . Digital signals can only take two values for example optical fibres take short pulses of light .
26
Analogue signals
Can take any value within a certain range , amplitude and frequency can vary continuously
27
What are the advantages of digital signals
Both weaken as they travel so they need to be amplified , they pick up interference or noise from other electrical disturbances and signals . When amplifying analogue , the noise is amplified too so the signal looses quality , digital signals noise is ignored so it remains high quality . Because digital waves are easier to tell apart as analogue waves are often of similar frequency more information can be transmitted along the same channel Digital signals can also be quantisation to transmit more information into one space , analogue signals loose lots of information if they are quantisation Digital can also be transmitted over a longer distance before it needs to be boosted but they are more difficult to make and require complex electronics
28
How do we see non luminous objects
They reflect light
29
How are mirrors used
To change the direction of ray of light e.g periscope rays from object strike first mirror at 45 degrees to the normal and are reflected at 45 degrees to the normal so are turned through 90 degrees which is repeated at the second mirror
30
How are images created by a plane mirror
Rays of light from objects strike mirror and are reflected to your eyes creating a virtual image as brain interprets rays of light as travelling i. Strait lines as rays of light do not actually pass ,
31
Properties of images in aplane mirror
The image is as far behind the mirror as the object is in front , it is the same size and is laterally inverted
32
Where does light travel fastest
Air and vacuum 300 million m/s , travels slower in water .
33
How is light refracted
When it travels from one medium to another it may change direction because the speed of light in one material is different to the speed of light in another. It will slow down and bend towards the normal is it eneters the glass and then leave the block , speed up and be refracted away from the normal A small amount is reflected from the boundary
34
What is refractive index
Every transparent material has one and it is Sin angle of incidence ---------------------- Sin angle of refraction
35
What is total internal reflection
If the angle of incidence is greater than the critical angle of that material , all the light is reflected from the boundary into the more dense medium
36
What happens if the angle of incidence is the critical angle
Refracted ray runs along the boundary | Critical angle for glass is 42 degrees and water is 49 degrees
37
How do you calculate the critical angle
Sin critical angle = 1 --- Refractive index number
38
What is the prismatic periscope
Uses prisms to totally internally reflect light and turn it through 90 degrees so the ray emerges parrales to the direction in which it was originally travelling This will be sharper and brighter than a periscope as some light is reflected in a periscope from the non silvered surface of the mirror creating faint images
39
How do binoculars work
Use prisms as reflectors for total internal reflection twice so it emerges from the prima travelling in the direction if originally came from
40
Who do optical fibres work
It has a central core of dense glass surrounded by a coat of less dense glass . Light eneters the inner core and strikes the boundary of the two glasses at an angle greater than the critical angle, no light escapes , it's internally reflected so the light follows the path of the fibre even if it's curved . Fibres can be bundled to carry sufficient light for images to be seen through them e.g. Doctors in endoscopes , light travels down fibres and illuminates object and light is then reflected by the object and travels up a second bundle of fibres creating an image of the object in the eyepiece
41
How do optical fibres transmit messages
Electrical signals converted into light energy by tiny lasers which send pulses of light to the end of optical fibres , light sensitive detector at the other end changes the pulses to electrical signals which flow into a telephone receiver
42
What is dispersion
White light passes through a prism and emerges as a spectrum because it's a mixture of colours and each colour travels through the prism at a different speed so it is refracted at a different angle so each colour emerges travelling at a slightly different direction, because the refractive index is different for each colour . Red speed is changed least so deviates least and violet speed is changed the most so it deviates the most
43
How does an object appear darker
If it absorbs some light so less is reflected
44
How are sound waves produced
Speaker cone pushes air molecules closer together creating a compression which push against neighbouring particles , behind the compression the particles are spread out which is call d a rare fraction . This creates a longitudinal wave .
45
How do waves enter brain
Enter ear strike eardrum and make it vibrate , the vibrations are changed into electrical signals which are detected by the bRain
46
What can sound waves travel through
Solids , liquids gases but not a vacuum because there are no particles to carry the vibration
47
Why does sound travel quicker in solids
Particles are closer together so they can transfer energy quicker
48
How do you measure the speed of sound with echoes
Ask friend to make a noise by banging two pieces of wood together. Stand distance away and use a stopwatch to time how long it is from when you see the pieces of wood banging together and when you hear the sound . To make this more accurate use echoes , stand 50m away from a large blank wall and clap two pieces of wood together and listen for the echo. Set up a rhythm so the echo comes between two claps . Time 20 claps and the sound would have travelled 2000m
49
Resonance tube and tuning forks
Strike a tubing fork of a known frequency and hold it above the open end if the tube , adjust water column so the loudest sound is heard , the first rensonance will be heard at 1/4 of the wavelength and calculate the sped of sound with frequency x wave length
50
Oscilloscope measuring speed of sound
Set signal generator to 1000hz start with microphones together and move one microphone away until it is one complete wavelength away from the first , shown by the oscilloscope being above one another , Measure the distance between microphones t get wavelength and use oscillope screen for frequency
51
What is resonance
Sound wave reflects and reflected wave reinforces the original wave creating à louder sound
52
What is a reflected sound wave called
An echo , angle of incidence is = to angle of reflection
53
How do ships use echoes
To discover depth of the water beneath them . This is called echo sounding . Sound waves are emitted from the ship and travel to the sea bed .equiptment on the ship detect the reflected sound waves . Depth of the sea is calculated from the time between sending the sound wave and detecting the echo .
54
Why can sound pass through doorways
Diffracted and spread out
55
What do strings of violin produced
Vibrate quickly and produce sound waves with a high frequency giving a high pitch Cellos vibrate more slowly and produce lower frequency waves with a lower pitch
56
What is audible range
People can only hear sounds that have a frequency higher than 20Hz but lower than 20 000 HZ. Sounds that vibrate higher than this are ultrasounds , sounds that vibrate slower are called infrasounds
57
What affects loudness of sound
Lots of energy transferred , vibrates with more amplitude and creates regions of very compressed air molecules which chatty lots of energy as they move away from the source which we hear as a loud sound . Softer sounds have less dense compressions
58
How is the time period show on an oscilloscope
Time taken for one complete cycle
59
What happens in flouresence
Uv absorbed and visible light emitted
60
Why do rectangular blocks not disperse light
Sides are parallel so the rays of light bend by the same amount when they enter and leave the block and emerge parallel whereas in a prim there are different boundarys
61
Total internal reflection
When light is incident at a boundary between materials at an angle greater than the critical angle causing the light to be reflected back at then kinda turn
62
What's wrong with sharply bending optical riveted
Some light will meet the boundary at an angle that is smaller than it equal to the critical angle so lots of light escapes the optical fibre
63
Critical angle
Angle of incidence that the angle of refraction is 90 degrees

Physics Year 11 (4 decks)

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