P5.3 Flashcards
What is angle of incidence and angle of reflection?
Angle of incodence is the angle between the ray and thr normal (normal to the boundary its hitting )
Relfection is angle from reflected ray and normal
REMEMBER ITS FROM THE NORMAL AND RAY NOT THE GROUND AND NORMAL
Law of reflection
Angle of incidence is always = to angle of reflection in any surface and wave
If drawing a wavefront diagram what should be remembered about the actual waves (wavefronts)
So draw your angle of incidence and refraction and normal but make sure the wavefronts are perpendicular to the path of the wave (angle of incidence thing)
The wavefronts are peaks from birds eye view
What is a virtual image
An image which appear to diverge from a point
- essentially inside a mirror
Diverge just means spread out
2) a virtual image cant be potjected on to a screen as inage is in the mirror.
How does reflection work in a mirror and so where do the light actually come from?
1) two rays coming out of image into mirror
2) these get angle of incidenced each, but then also extended out beyond in the mirror
3) where they meet is the virtual object
Although it seems that the rays are coming frim the virtual inage they actually coming from the object, which is just getting reflected into your eyes…
What three things can happen when a wave meets a medium
What makes one of these happens
1) transmitted across, the wave isnt changed
- hiwever could become refracted( change direction and speed)
2) energy absorbed so doesnt go through the material
3) reflected
The properties of wave and material involved
What is refraction in a wave
When a wave changes direction from one medium to other
- this happens because wavespeed changes and this means the wavelength will change too as frequency is constant
What causes the amount of energy transmitted absorbed or relfected
The media
Distance wave came frim
Wavelength it had
How do EM waves interact going into dense and out of dense mediums
What bout normal incidence
1) going into dense it slows down meaning wavelength decreases and bends TOWARDS NORMAL
2) going out wavespeed increases and bends away FROM NORMAL as wavelength also increases
When normal incidnece haopens it doesnt refract like that but speed changes. SLOWS DOWN AT ONCE
Now when looking the rays are coming from a different place thus looks like straw is bent
How does wavefronts move from deep to shallow?
Shallow water they live more slower meaning wavelength decrease and bend towards normal
Therefore they becomes more bunched up
What is relationship between wavelength and refaction and how does that make a rainbow
What dispersion
What type of medium specifically need and why
How can you show the differnt wavelengths refact differently in a quick practical?
The smaller the wavelentgh the bigger the refraction. This is because they slow down more so smaller wavelength and bend more to normal
When the white light is spread out
When white light is refacted, its different wavelengths will mean it will refract differently and split. For example red bends the least but violet bends more. Red has higher wavelength so regact less. Different colours have different wavelengths so thats how, they make rainbow
2) a prism, as it doesnt have parallel boundires meaning angle of incidence isnt the same both times and the wavelengths are actually refracted differently
3) ray block with filters that shine only red light, trace incidence refraction and same with blue, should see they refact differently
How does colour work and how do filters work
-how does object behind colour filter look
Different objects absorb and transmit and reflect colours differently. An object that absorbs all frequencies but reflects red will be seen as red.
This is the case for opaque objects, they dint transmit lightbjust absorb and relfect
All light ha sky’s own wavelength, but you can make them to except for red green blue, if you see yellow it relects combination if both
- eg white objects reflect rgb , black absorbs all of them (no light)
2) Colour filters absorb all light and transmit the one you want out, so you see that.
- if a red filter and green filter put next to each other you see black as now together all colours are filtered
- now if you put red hat behind red filter it is red but if blue then black because light reflected off blue is absorbed and lack kf light = black
(If it is say cyan filter will let out cyan and primary colours that make up cyan)
Scattered vs specular reflection
Why in scattered can you not see virtual image
Dark vs light cloud (scattering/ absorb)
Specular is regular reflection such as plane mirror- this is why you see images as virtual
Scattered is when scatter is diffuse. Bumbos or uneven surface means light reflects unevenly. Law of reflection still applies but rays reflect at different angles respectively.Meaning an image cant be formed
However some particles scatter everythint so it seems white and doesnt matter. Or they absorb everything and seems black
How does concvex lens (converging) lens work and how to do ray diagrams
It refracts to a focal point
1) draw image, parallel ray goes ti middle and refracts through the focal point. ( this point in which laralle lines refacted meet up at)
2) diagonal line goes theough that doesnt bend. Where these meet makes a REAL image, inverted however and diminished
What happens when convex lens changes its distance and how can fore happens?
2F and beyond
F to 2f
Less f
Diverge? Virtual
If beyond 2F and 2F
- real, inverted but diminished or the same height here
If F to 2F
- real inverted magnified
If less than F
- VIRTUAL upright magnified, this how magnifying glass works
- goes through focal and middle, rays extened to produce virtual image on left
Remember real image is image which is formed by light rays that seem to have diverged by there.
How does concave diverging lens work
Now matter the object what happens in a concave lens?
How to draw ray diagram
- draw parallel lines and how they refract in kens and out
- extend these lines to form a virtual focal point, the point where it seems they diverge from
1) always VIRTUAL, upright and dininished
2) parallel line hits and refracts outwards such that virtual line meets principal focus
- diagonal goes through
- where they meet is the virtual inage that cant be projected onto a screen where rays appear to diverge from this is the top of the screen… the
How does lens correct vision
Short sight= can only see short= lens too strong/ long= image formed before the retina= CONCAVE NEEDED diverge then correctly refract in
Long sight= fan only see long= lens too weak or short= image formed behing the retina=
CONVEX LENS NEEDED refract in a bit then refract in some more
Remember for short they arent parallel lines they come from a point
What is some info on sound waves?
Longtidunal? What thos mean etc
1) longitudinal, regions where compressed are compressions and other is rarefactions
- waves oscillate same direction as energy flow
- caused by vibrations
How does the ear hear ?
1) the outer ear (pinna and auditory canal) gathers soundwaves and directs them yo the ear drum, which CAUSES IT TO VIBRATE.
2) As ear drum vibrates it makes the tiny bones in ear ossicles to vibrate.
3) these act like levers and amplify vibrations and pass it to inner ear of SEMICIRCULAR CANAL and through OVAL WINDOW to the COCHLEA
4) snail like cochlea have hairs that attach to sound hearing cells and convert to an electoval signal sent down auditory nerve and processed by the brain…
Summary
1) pinna and auditory canal direct soundwave to drum which vibrates, casues ossicles to vibrate act like lever and amplify sound
2) goes through semicricular canal and oval window to cochlea
3) cochlea has hairs that connect to sound cells that send nerve to auditory to brai
What happens to hearing when you get older and what is a natural frequency?
What is human healthy frequency
Natural frequency: frequency applied that is the same, they will vibrate with a big amplitude- resonance
1) as you get older wear and tear of shorter hairs in cohclea mean you cant hair the higher frequency. The range of frequency we hear depends on the different lengths if these hairs, as they each have different NATURAL FREQUENCIES (and so certain frequencies can only cause each to resonate like so).
- as we have differenr lengths we can hear diffeeent feequencies
Loud as well
20hz 20000hz
What is ultrasound and how we can use it?
1) any frequency higher than 20khz
- when an ultrasound wave meets a boundary it is transmitted but some reflected too. This time delay of reflection can be used to calculate distance if speed of wave is known IN THAT MEDIUM
Because it is different in each medium
Why do we use uktrasound over d rays
Safer than x rays and not ionisjg
Okay si how we use uktrasound in pregnancy scans
What about other soft tissue
- uktrasound passes through the body but is partially reflected by different mediums
- these include the muscles in woman stomach, or the fluid in her womb or even the skin if the foetus
- if we know speed of ultrasound in these DIFFERENT mediums, then you can work out distances , and these are processed by computer to make image
2) similarly can be used to see kidney stines, liver or bladder things
Summary
1) ultrasound goes through body but is reflected by different mediums of tissue and substance in body
2) knowing the speed ultrasound travles i. These mediums we can work out the distances which can be processed hy a computer to make an image
How can ultrasound be used to detect cracks in industry?
What about sonar what need to remember
Ultrasound is usually reflected by the far side of an object
If there is a crack another will reflect sooner, thus there is a crack
2) divide by 2
Finally how can sound be refracted as in change direction as a result of a change of velocity
Also how can sound trigger vibrations in solids, why quicker based off particle models
Sound travels faster in hot air and solids and liquids
When sound travels faster, wavelength increases so it bends away from normal
Cause particles to vibrate that cause other particles to vibrate. Because particles so close and vibrations easilly passed between them, sound travels quicker in solids
What is relationship between frequency and litch and amitude and volume
High frequency = high pitch
Small amplitude is quiet
Large amplitude= loud
What is outer esr?
Inner ear
Outer ear is pinna and auditory canal
Inner ear is semicircular cnal and oval
