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REFRACTION
Humans see objects when visible light is reflected off
these objects and enters the eyes.
HOW DO WE SEE?
INTERESTING…
Have you ever noticed that the sun
seems to change colour as it sets?
Or how your legs look different when you
walk in clear water?
This occurs because of the bending of
light!
Light travels in straight lines AS LONG
AS it is traveling in ONE uniform
material.
MEDIUM
The substance or material that light is travelling
through (e.g. water, air, glass, oil)
REFRACTION IS...
angle of
incidence
angle of
refraction
incident
ray
refracted
ray
• the change in direction of light as it moves from
one medium to another…”__________________”
qi angle of incidence
qr angle of reflection
qR angle of refraction
REFRACTION
WHY DOES REFRACTION
OCCUR?
Light travels in a straight line
When light travels from one medium to another,
the speed of light changes.
The result is a change in direction of the light.
e.g. Speed of light in air: 3.00x108 m/s
Speed of light in glass: 2.00x108 m/s
WHY DOES REFRACTION
OCCUR?
• air is less ______ than
glass
• light travels _______ in air
• light travels ________ in
glass
RULES OF REFRACTION
1. The incident ray and the refracted ray are on
___________ sides of the normal and opposite sides of
the boundary between the two media (e.g. where
air/water meet)
RULES OF REFRACTION
2. Light bends _________the normal when it travels from
a less dense to a more dense medium (slows down).
3. Light bends ________ from the normal when it travels
from a more dense to a less dense medium (speeds
up).
Less dense to more dense.
More dense to less dense.
FST
Fast to Slow, Towards normal
Funny Science Teachers
SFA
Slow to Fast, Away from normal
S F Alot
REFRACTION
CONDITIONS NECESSARY FOR
REFRACTION
light must change _________ (change speed when
crossing the boundary)
light must approach the boundary at an ___________
INDEX OF REFRACTION
The _________ of the speed of light in a vacuum (c) to the speed of light in a given material (v).
where…
n is the index of refraction
c is the speed of light in a vacuum (3.00x108m/s)
v is the speed of light in the other medium in metres per second (m/s)
Medium Index of Refraction (n)
air/vacuum 1.00
ice 1.31
pure water 1.33
ethyl alcohol 1.36
quartz 1.46
vegetable oil 1.47
olive oil 1.48
acrylic 1.49
glass 1.52
zircon 1.92
diamond 2.42
gallium phosphide 3.50
Table 1 – Indices of Refraction
EXAMPLES
1. The speed of light in sodium chloride (salt) is
1.96x108m/s. Calculate the index of refraction for
sodium chloride.
2. Calculate the speed of light in olive oil.
3. What is the index of refraction of a substance in which
the speed of light is 8.57 x107 m/s? What substance
could this be?