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Refraction of light
1 John says,
‘ When hunting a fish under water, you should aim your spear directly at the fish.’
Do you agree?
Yes, of course.
No, because the fish is actually located somewhere else.
No, because size of objects changes when they are put under water.
2 When sunlight falls on the water surface, which of the following occur(s)?
It is reflected back to the air.
It refracts into the water.
It is absorbed by water and turned into heat.
airglass
Refraction is the bending of light
when the light passes from one medium to another.
Introduction
airglass
Useful words to describe refraction of light
normal
incident ray
angle of refraction
angle of incidence
refracted ray
Introduction
airglass
• e.g. from air to glass
• Light is bent towards the normal.
incident raynormal
refracted ray
From a less dense to a denser medium
Introduction
airwater
From a denser to a less dense medium
• e.g. from water to air
• Light is bent away from the normal.
incident rayrefracted ray
normal
Introduction
airglass
incident ray
refracted ray
normal
airglass refracted ray
normal
• The incident ray,the refracted ray,and the normalall lie in the same plane.
Laws of refraction
Example 3
Applying Snell’s law, 1.33 sin w = 1 sin 30 sin w = sin 30/1.33
w = 22.1
airwater
30
nw sin w= na sin a
= 0.376
22.1
Q1 A boy shines a torch under…A boy shines a torch under water as shown.
Which one shows the correct path of the light ray?
A Path X.B Path Y.
C Path Z.
D All of them.
Q4 True or false: When light is…
True or false: When light is incident on a surface along the normal, only refraction occurs; there is no reflection.
(T/F)
Q5 Statements:...
1st statement 2nd statementLight is bent towards the normal when it passes from air to glass.
Glass has a greater refractive index than air.
true? true? true? true?
YesYes YesYes
4 Examples of refraction of light
a Bent chopstick
• The chopstick appears bent because of refraction
4 Examples of refraction of light
b Shallower in water• The depth that the object is
actually at is called the real depth.
O
Ireal dept
h
Simulation
4 Examples of refraction of light
c Flickering objects in hot air
• The object you see through the unstable hot air appears blurred and flickering.
Q1 True or false: Light slows…
True or false: Light slows down when it enters a material from air.
(T/F)
Q2 True or false: The refractive…
True or false: The refractive index cannot be smaller than 1.
(T/F)
Q3 True or false: If light travel…
True or false: If light travel at the same speed in all materials, refraction would still occur when it passes from air to water.
(T/F)
Q4 True or false: If the speed of…
True or false: If the speed of light in raindrop is equal to that in air, there would be no rainbows. (T/F)
