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6 Waves Flashcards

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1
Q

transverse wave

A
  • oscilations are perpendicular to the direction of energy transfer
  • most waves are transverse
  • all electromagentic waves, ripples and waves in water, a wave on a string
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2
Q

longitude waves

A
  • ossillatyions are parallel to the direction of energy transfer
  • sound waves and shock waves
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3
Q

what is the wavelength of a wave

A
  • distajce between the same point on two adjacent waves
  • eg. between peaks or troughs
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4
Q

what is the amplitude of a wave

A
  • maximum displacememnt of a poitn on the wave from its undisturbed position
  • from the x axis to the top of a wave
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5
Q

what is the frequencey of a wave

A
  • number of complete waves passing a certain point per second
  • measure in Hz, 1Hz = 1 wave per second
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6
Q

period =

A

1/frequncey

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7
Q

wave speed (v) =

A

frequencey (f) x wavelngth (λ)

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8
Q

measurign water ripples experiment

A
  1. Set up the ripple tank with about 5 cm depth of water.
  2. Adjust the height of the wooden rod so that it just touches the surface of the water.
  3. Switch on the lamp and motor and adjust until low frequency waves can be clearly observed.
  4. Measure the length of a number of waves then divide by the number of waves to record wavelength. It may be more practical to take a photograph of the card with the ruler and take measurements from the still picture.
  5. Count the number of waves passing a point in ten seconds then divide by ten to record frequency.
  6. Calculate the speed of the waves using: wave speed = frequency × wavelength.
    risks and hazards:
    Electrical components near water - shock and damage to components - secure electrical components before adding water taking care not to splash
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9
Q

measuirng waves on a strign practical

A
  1. Attach a string or cord to a vibration generator and use a 200 gram (g) hanging mass and pulley to pull the string taut as shown in the diagram. Place a wooden bridge under the string near the pulley.
  2. Switch on the vibration generator and adjust the wooden bridge until stationary waves can be clearly observed.
  3. Measure the length of as many half wavelengths (loops) as possible, divide by the number of half wavelengths (loops). This is half the wavelength, doubling this gives the wavelength.
  4. The frequency is the frequency of the power supply.
  5. Calculate the speed of the waves using: wave speed = frequency × wavelength.
    risks and hazards :
    Cord snapping - damage to eyes - eye protection / safety screen
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10
Q

how can you use an oscilloscope to measure the speed of sound

A

-turn on a speaker attached to a signal genertaor
- set up oscilloscope so the detected waves ayt each microphone are shown as sperate waves
- start with both microphones next to the speaker then slowly move one away until the two waves are aligned on the displaybut hav emoved one wabelgth away from eachother
- meaaeure the distance between th microphones to find one wavelngth
- use v =fλ to find the speed passing through the air
- speed of sound roughly 330m/s so results shoudl be roughly the same

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11
Q

what happens when a wave arrives at a boundary

A
  • absorbed by the material - transfers energy to the materaial’s energy store
  • transmitted - carry on travelling through the new material - refraction
  • reflected
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12
Q

explain how to draw a simple ray diagram for specular reflection

A
  • daw a boundary
  • draw the incoming ray, where it meetsdraw a nromal which is 90 from the boundary
  • where the incomign ray and boundary meet is th eincidence point
  • angle of incidence is from incomign ray to normal
  • reflected ray will be the same as incomign ray
  • angle of incidence=angle of relection
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13
Q

what is specular relfection

A
  • happens when a waeve is relfected in a signle direction by a smooth surface
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14
Q

what is diffuse relfection

A
  • when a wave is relfecte don a rough surface
  • refleted rays are svattered in lots of directions
  • hapens because normal is different for each incomign ray so angle if incidnec e is different for each ray
  • when ligth reflected by a rough surface the surface appears matte
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15
Q

what happens when a wave crosses a boundary

A
  • if comes at an angle, direction changes
  • speed up if enters a less dense medium - bend away from the normal
  • slow down if enters a denser medium - bend towards the normal
  • wavelngth changes but freuqmey stays the same
  • if wave travelling along the normal won’t refract btu will chand speed
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16
Q

how to construct a ray diagram for a refracted light ray

A
  • draw the boundary between the two material and the nromal perpendicular to the boundary
  • draw incident ray that meets th enormal at the boundary, angle between ray and normal is angle of incidence
  • ## draw refracetd ray on other side of boundary, if second material denser draw it towards the normal so angle of refraction smaller, if less dense opposite
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17
Q

investigatingrefraction

A
  1. Set up a ray box, slit and lens so that a narrow ray of light is produced.
  2. Place a 30 centimetre (cm) ruler near the middle of a piece of plain A3 paper. Draw a straight line parallel to its longer sides. Use a protractor to draw a second line at right angles to this line. Label this line with an ‘N’ for ‘normal’.
  3. Place the longest side of a rectangular
    acrylic polymerblock against the first line. With the normal near the middle of the block, carefully draw around the block without moving it.
  4. Use the ray box to shine a ray of light at the point where the normal meets the block. This is the incident ray
  5. The angle between the normal and the incident ray is called the angle of incidence. Move the ray box or paper to change the angle of incidence. The aim is to see a clear ray reflected from the surface of the block and another clear ray leaving the opposite face of the block.
    - Using a pencil on the paper, mark the path of: the incident ray with a cross, the reflected ray with a cross
    the ray that leaves the block with two crosses - one near the block and the other further away
    - Remove the block. Join the crosses to show the paths of the light rays.
    - Repeat steps 2 to 7 for a rectangular glass block.
    - Measure the angle of incidence, angle of refraction and angle of reflection for each block.
    risks and hazards:
    - Ray box gets hot- Minor burns-Do not touch bulb and allow time to cool
    - Semi-dark environment - increased trip hazard- ensure environment is clear of potential trip hazards before lowering lights
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18
Q

whast the Electromangetic spectrum

shortest to longets wavelength

A

radio waves
microwaves
infrared radiation
visible light
ultra violet
x-rays
gamma rays

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19
Q

as you go up the em spectrum …

A

the wavelngth gets smaller and the frequencey increases

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20
Q

puropses of microwaves

A
  • communication to and from satelites - signal from a transmitter is transomitted to space, picked up by sateltite reciever dish orbitting earth, transmits the signal to a different direction of earth, picked up by satelite dish on earth
  • can pass easityl through the atmosphere
  • microwaves - different wavelngth though, microwaves abrobed by water molecules in food, pemetrate a couple cm itno food before beign absorbed and transferrign energy to water moelcules caauign it to heat up, water molcules then trasnfer this enrgy to the rest fo the molecule sin the food
21
Q

uses of radio waves

A
  • wavelngths longer than 10 cm
  • used for communication - longwave radio can be transmitted around the earth since they bend around the earth
  • shortwave radio also transkitted aorund the world are relffcted from the ionsphee
  • short wave radui yused over short distances, eg headphones and phone
22
Q

wat are EM waves made up of

A
  • oscilatting electric and magnetic field - alternatibe currents amde up of oscilattng charges
  • as the charges oscillate they produce osciallting electric adn magentic fields ie. EM waves
23
Q

hwo are radio waves made

A
  • using an A.C in an elcetrical current,
  • object whihc charges oscialte to create radio waves is called a transmitter
  • when tranmitted radio waves reach a reciever, radio waves are absorbed
  • energy carried by the waves is transferred to the electrons in he material of the reciever
  • this energy causes electrins to oscialte and if reciever part of a complete circuit, generates an AC
  • the current has the same frequencey as radio wave that generated it
24
Q

uses of infra red radiation

A
  • used to increase temp or monitor
  • infrared cameras detect IR radiation to mnitor, truns IR to electrical signal displayed on screen, th ehooter an bject the redder/briughter it looks
  • abosrbing IR causes objects to get hotter - asbrobed by food to be cooked
  • electric heaters - contain long poiece of wire that heats up when current flows through, emits a lot fo IR which is abosrobed by objects and air in room, energy tasnfered bu IR waves to thermal enrgy stores casuign temp to increase
25
Q

uses of visible light

A
  • to see duh
  • optical fibres - thing glass or plastic fibres that carry dataa over logn distance as pulses of visible light
  • lihgth rays bounce back and forth until reach end of fibre
26
Q

uses of UV

A
  • flourescent - UV abosbred and then visibel light is emmited
  • security pens used to mark property, write with invisibel ink thatwill glow under UV
  • UV produced by the sun so cna guev tans
  • tannign salons use UV lamps
27
Q

Uses of X-rays

A
  • pass easily through flesh but not easily through denser material like bones or metal
  • can be used to giev to cancer patients to kill cancer cells
28
Q

uses of gammas rays

A
  • used to kill cancer cells
  • cna be used as a medical tracer- gamma emtting source is injected into the patient, and its progree is followed aroudn the body- gamma is highly penetratign so can easily be detetcted
29
Q

danger of high freuqncey waves

A
  • transfer lots of energy which can cause damage
  • x-rays and gamma rays are ionising so can cause genetic mutations, cell destruction or cancer
  • UV rays, damage surface cells whci cna lead to sunbuns, skint o age prematurely, blindness and increased risk of skin cancer
30
Q

properties of convex lenses

A

axis - line passign throught he middle of the lens
- bulge outwrds
- make rays of ligth to converge at the principal focus - where rays hitting the lens parrallel to the axis meet, meet after lens
- incident ray parrallel to the axis refracts through the lens and passes through the principal focus on the otehr side
- incidne tray passign through th e proincipal focus refracts throught th lesns anf travels parallel to the axis
- incidnet ray passing through thr ecntre of the lens carries on in the same direction

31
Q

properties of convex lenses

A
  • caves inwards- parrallel rays of ligth to diverge
  • principla focus poitn where rays hittign thr lens parallel to the axis apprar to all come from, meet up before lens
  • incident ray paralle to axis refracst through th lens and travels in line with principal focus an aincident ray passing through the lens twards the principal focus tefracts through the lens and travels arallel to the axis
  • incident ray pasign through the centre of the lens carries on in th same direction
32
Q

how do you describe image

A
  • wetehr its real or virtual
  • magnified or diminshed
  • uprigth or inverted
33
Q

how to draw a ray diagram for a convex lens

A
  • pick a point on th top of the object nd draw a line parrallel to the x axis joing the y-axis
  • draw line from top of the object through the centre of the graph
  • draw a line fromt h lien draw parallel through the prinicpal focus
  • where the two liens converge will be the top of the image
34
Q

how to draw a ray diagram for a concave lens

A
  • always virtual, uprigth and diminished
  • pick a point on th top of the object nd draw a line parrallel to the x axis joing the y-axis
  • draw line from top of the object through the centre of the graph
  • draw ray form principal fpcus- dotted before reaches lens
  • where the liens meet is wehre the top of the obejct is
35
Q

how do colour filters work

A
  • absorbs all otehr wavelgths aprt form that colour
35
Q

why do objects look blakc when shone with ligth form a filter

A

eg. if red filter, and blue object, only red light passes through, no blue ligth for blue object to reflect so abosrobs red and looks red due to abesnece of bleu light

35
Q

magnification =

A

image height/object height

35
Q

practicsl to investigate IR emmission with a leslie cube

A
  1. Place a Leslie cube on a heat-resistant mat. Fill it, almost to the top, with boiling water and replace the lid.
  2. Leave for one minute. This is to enable the surfaces to heat up to the temperature of the water.
  3. Use the infrared detector to measure the intensity of infrared radiation emitted from each surface, or the temperature of the surface. Make sure that the detector is the same distance from each surface for each reading.
  4. record results for each side
  5. plot a bar chart
  6. evalute which best emmitter of IR radiation
36
Q

what is a blakc body

A

a hypotehticla object that:
- absorbs all raditaion that fall on it
- woudl not reflect or transmit any raditation

37
Q

how does a blakc body diagram work

A

The hotter the object the shorter the peak wavelength emitted.
area under the line is the total energy radiated per unit of time per unit of surface area by the object at that temperature
he hotter the object the more energy, or power is radiated by the blackbody.

38
Q

what are spund waves

A
  • casued by vibrating objects
  • passed through compressiosn and refractions
  • travels fastest through solid
  • longitudinal waves
39
Q

hwo do ears work

A
  • soudn wave reaches ear drum casuign it to vibrate
  • vibratiosn pass on through tiny bomes called ossicles through semicircular canals and to the cochlea
  • cochlea turns these vibratoions into eletcricla signals which get sent to your brain
40
Q
A
40
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40
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41
Q

what is ultrasound

A
  • sound with frequencey higher thsn 20,000 Hz
  • partially relect at a boundary, some waves are refracted some are reflected
42
Q

different seismic waves

A
  • P-waves, longitudinal travel through solids and liquid and fasr
  • ## S-waves transverse, can;t travel through liquid or gas and lsower
42
Q

what is ultrasound used for

A
  • medicla imaging- can pas through the body whenerver reahc a boundary some of the wave is reflected back and detected, timing and ditribution of the waves is processed to create an image
  • industrial imaging eg.findign flaws in objects - ultrasound wave enter a material usally reflect bu the far side of the material, if there is a flaw the wave will be reflected sooner

physics (4 decks)

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