reflection and refraction notes
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7/28/2019 Reflection and Refraction Notes
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Reflection and Refraction Notes
Law of Reflection
How large a mirror does one need to see one’s whole face?
Microscopic
View of an
Uneven
Surface
“Diffused
Reflection”
“o”: object
“i”: image
Object size, ho = Image size, hi Object distance, d o = Image distance, d i
for a plane mirror
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Answer : You only need a mirror ½ the length of your face.
Law of Refraction
When light travels from one medium to another with a different refractive index, n, the light ray travels
with a different speed and so it changes direction.
A Model
Refractive index, n, indicates how quickly light travels in that medium…larger n = slower
⏟
⏟
Example: Determine the angle of refraction as light travels form glass into water with an angle of
incidence of 20.0°.
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d
() ()
()
()
A similar result happens for light rays:
Answer : The hunter should aim his spear at C, because the light reflecting off of the fish is refracted as
shown below. Our eyes perceive light as travelling in straight lines, so the fish appears to be at B even
though it is really at C.
Where does the hunter
aim his spear if the fishappears as it is shown?
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Questions on Refraction
Light is incident on a glass prism (n = 1.50) and the incident angle, θ i is 35°. Determine
a) the angle of refraction, θ r at A.
b) the angle of incidence, θ i at B.
c) the angle of refraction, θ r at B.
(nair = 1.0003)
a) At A:
b) At B: ( )
c)
at B:
Critical Angle and Total Internal Reflection
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Question: Determine the critical angle for water (nwater = 1.33, nair = 1.00).
Glass or Diamond?
nair = 1.00
nglass = 1.50
ndiamond = 2.42
A diamond sparkles more as the light
reflects internally more than glass
does. Different colours have slightly
different refractive indices and thus, a
spectrum of colour is often refracted
out of the diamond - dispersion.
What is a mirage?
( )
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Since we always see light rays travelling in straight lines…The sun and clouds appear as a reflection as
though there is some water on the ground. This illusion is called a MIRAGE.
How is a rainbow formed? Read up about it.
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