oscillations are perpendicular to direction of energy transfer
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what are longitudinal waves
oscillations that are parallel to the direction of energy transfer
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what is the law of reflection
angle of incidence= angle of reflection
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what is specular reflection
=clear image
flat boundary = normals are in same direction
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what is diffused scattered reflection
bumpy boundary
= normals will be all different
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what is refraction
when waves change direction as they pass from one boundary to another
higher density=> slower wave=> bends towards normal
less dense=> faster wave=> bends away from normal
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what are compressions and what are rarefactions
wave length in diff. mediums
regions where vibrating particles are closest
regions where vibrating particles are furthest apart
high mediums= w. longer as sound speeds up
low density mediums= shorter, as slow down
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processes of hearing
ear canal=> ear drum and vibrate=> transmitted along ossicles=> semi-circular canals=> cochlea converts vibrations into electrical signals=> brain
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what is ultrasound
sound that vibrates at frequencies +20,000Hz
(i.e sonar in bats/ echo location)
(electric devices=> electrical oscillations converted to u.s waves)
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use in ultrasound machines
foetal scans= fire u.s at foetus, some waves reflected back (diff. mediums) to device, and echos processed.
check baby's health
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what are seismic waves
and what do we uses seismometers for
p-waves (l)= faster and travel through solids/liquids
s-waves (t)= travel through solids
to detect how long it takes for waves to travel from earthquake site to diff. parts of the world
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how to seismic waves work
reflected, transmitted or absorbed=> refracted, change in density=change in direction=> p-waves only for (for l)=> s-waves can only pass through solid region of Earth's structure
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the 3 refractive index and critical angle rules
1) if a.o.i < c.a= light refracted away from normal
2) if a.o.i = c.a= light refracted at 90 degrees to the normal
3) if a.o.i > c.a= no refraction occurs
sin(c)= 1/n
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what is the focal length
distance between f and the centre of lens
shorter f.l= more powerful the lens
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real images vs. virtual
r= light rays actually do come together to form the image
v= formed when the light rays don't come together where the image appears
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what are radio waves used for
bonds holding molecules together oscillate
transmitter=> oscilloscope
diffract around the Earth's curved surface = long waves= huge distance
reflect off ionosphere= short waves = long or short distance (Bluetooth)
v. short waves= transmitter=> receiver
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what are micro and infrared waves used for
communication
m= are but aren't absorbed by water (satellites and ovens)
I= in cameras (emitted from all objects w. thermal energy), ovens (emit= heat food by transferring heat energy)
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what are visible light and UV waves used for
v= communications (optical fibres)
U= sun beds (fluorescence=> UV light is absorbed=> energy re-emitted as visible light)
security pens= shine UV light on to detect forgery, or sterilise water to destroy microorganisms (u= ionise)
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what are x-rays and gamma waves used for
ionise
x= detect broken bones/ other diseases (wear lead apron or leave room)
g= medical imaging and treat cancer (radiotherapy), sterilise medical equipment and food (kill microorganisms)
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Other cards in this set
Card 2
Front
what are longitudinal waves
Back
oscillations that are parallel to the direction of energy transfer
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