P1.5 waves

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  • Created by: elisha.ks
  • Created on: 18-03-17 12:00
what do waves do
transfer energy from one place to another without transferring nay matter
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what is frequency
number of waves passing a point per second/ number of waves produce by a source per second
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1Hz =
1 wave per second
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transverse waves and examples
oscillations are perpendicular to direction of energy transfer, light + EM waves, ripples on water, slinky up + down
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longitudinal waves and examples
oscillations are parallel to direction of energy transfer, show areas of rarefaction+compression, sound waves, ultrasound, seismic(shock)waves, slinky spring pushed
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what can mechanical waves be
either transverse or longitudinal
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units for speed, frequency, wavelength
m/s, Hz, m
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what's the speed of EM waves
3 x 10^8
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what happens when waves arrive at an obstacle/ meet a new material
their direction of travel can be changed
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reflection
allows us to see objects (light bounces off object into eyes)
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what happens when light reflects off an uneven surface like paper
it reflects off at different angles
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what happens when light reflects off an even surface
it's all reflected at the same angle and you get a clear reflection
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what is the normal
a construction line perpendicular to angle of reflection
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describe the image produced in a plane mirror
same size as object, same distance from mirror, virtual, upright, laterally inverted
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what is diffraction
waves spread out at edges when they pass through a gap or pass an obstacle, amount of d depends on size of gap relative to wavelength
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what causes more spreading
narrower gap or longer wavelength
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explain a narrow gap
same order of magnitude as wavelength (ie same size), light has small wavelength so needs small gap to be diffracted
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what is refraction
when a wave crosses a boundary between 2 substances, it changes direction (eg glass to air)
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what happens when light shines on a window pane
some is reflected, most passes through and gets refracted
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when do waves refract
only when they meet a new medium at an angle
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what happens if the wave travels along the normal
they'll change speed but not direction so aren't refracted
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explain EM waves
7 types w different freq/wl/energy so have different properties, vary in wl from 10^15m to more than 10^4m, all travel at 3 x 10^8 m/s in a vacuum
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7 groups descending from highest wavelength
radiowaves, micro waves, infra red, visible light, ultra violet, x-rays, gamma rays
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shorter wavelength =
higher freq. and higher energy
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long-wave radio waves
can be transmitted across long distances: they diffract around curved surface of earth and can diffract around hills/into tunnels
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explain diffraction effect
makes it possible for radio signals to be received even if the receiver isn't in line of sight of transmitter
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short-wave radio waves
used for TV/FM radio, need to be in direct sight of transmitter for reception, can be received at long distances from transmitter
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how are they received at long distances
reflected in the ionosphere (electrically charged layer of atmosphere)
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medium-wave radio waves
can also reflect from ionosphere, depending on atmospheric conditions and time of day
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microwaves
communication, can easily pass through earth's water atmosphere (radio waves cant)
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explain satellite process
signal from transmitter is transmitted into space where it's picked up by the receiver dish orbiting earth. Satellite transmits the signal back to earth in a different direction and received by satellite dish on ground
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mobile phones
calls travel as microwaves between phone and nearest transmitter
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disadvantage
some wavelengths are absorbed by water molecules, if this is in cells they can start to cook, some believe this can damage your health
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infrared waves
used for wireless controls, work by emitting different patterns of infrared waves to send different commands to an appliance
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optical fibres
can carry data over long distances quick, use infrared+visible light, signal carried as pulses of light/infrared radiation, reflected off sides of narrow cone from one end of fibre to another
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lens in camera
to focus visible light onto a light-sensitive film or electronic sensor
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lens aperture in camera
controls how much light enters camera
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shutter speed in camera
determines how long the film/sensor is exposed to light
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what does varying these things do
allow photographer to capture as much light as they want
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uses of radio waves, microwaves, infra red and visible light
communication, satellite communication/phones, remote controls/optic fibres, photography
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sound waves
caused by vibrating objects, the mechanical vibrations are passed through the surrounding medium as a series of compressions, type of longitudinal wave
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how we hear sound
sometimes sound travels into the ear and reaches the eardrumm
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how does it travel in different types of medium
faster in solids-liquids-gases, can't travel in vacuums because there are no particles (ie space)
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when are they reflected, how is it different in a furnished room to an empty room
reflected by hard, flat surfaces, in full room they absorb sound quickly + stop echoing
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echoes =
reflected sound waves, delay between original+echo, echoed sound waves have to travel further so take longer to reach ears
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when do sound waves refract
as they enter different media, in denser materials they speed up
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high frequency sound waves =
high pitched (short wavelength)
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frequency =
number of complete vibrations per second
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loudness depends on
amplitude, bigger amplitude=louder sound
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Other cards in this set

Card 2

Front

what is frequency

Back

number of waves passing a point per second/ number of waves produce by a source per second

Card 3

Front

1Hz =

Back

Preview of the front of card 3

Card 4

Front

transverse waves and examples

Back

Preview of the front of card 4

Card 5

Front

longitudinal waves and examples

Back

Preview of the front of card 5
View more cards

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