2 refraction of light
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REFRACTION OF LIGHT
A pencil appears bent or broken when it is partially immersed in water
These are two situation that show the effect produced when light travels from one medium to another
The effects are due to the change of direction of light when light travels from one medium to another.
Refraction of Light• Refraction of light is the bending of a
light rays at the boundary as the rays travel from one medium to another.
• Light rays bend towards the normal when the rays travel from a less dense medium to a denser medium (eg: water to glass)
• Light rays bend away from the normal as it travels from a denser medium to a less
dense medium.
less dense
denser medium
i
r
i = angle of incidence
r = angle of refraction
i > r
Normal lineincident ray
refraction ray
less dense
denser medium
i
r
i = angle of incidence
r = angle of refraction
Normal lineincident ray
refraction ray
• Light rays bend towards the normal when the rays travel from a less dense medium to a denser medium
• Light rays travel much slower in a denser medium
air
kaca
air
water
denser medium
less dense
i
r
i = angle of incidence
r = angle of refraction
i < r
Normal lineincident ray
refraction ray
• Light rays bend away from the normal as it travels from a denser medium to a less dense medium.
• Light rays travel much faster in a less dense medium
denser medium
less dense
i
r
i = angle of incidence
r = angle of refraction
incident ray
refraction ray
air
glass
air
water
When light ray travels from one medium to another, its speed changes. The change in speed of the light ray cause the change of its direction.
ExperimentAim:
To investigate the relationship between the angle of incidence i and the angle of refraction r.
Inference:
The value of sin r is manipulated by the value of sin i
Hypotesis:
The greater the value of sin i the greater
will be the value of sin r.
Aim:
To investigate the relationship between the angle of incidence i and the angle of refraction r.
Inference:
The value of sin r is manipulated by the value of sin i
Hypotesis:
The greater the value of sin i the greater
will be the value of sin r.
Refractive Index
For a light ray travels from vacuum (or air) into a given transparent medium, the ratio of is is always constant.
Snell’s Law,
Refraction index, n = Sin i Sin r
Sini
Sinr
Refractive Index
Laws of Refraction
58.7
40
water
air
30
19.2
air
kaca
60
40.6
water
air
75
40.4
perspex
air
Example
1.
3.
1. 2.
4.
n = speed of lights in the air @ vacuum speed of lights in the medium
Refractive Index and Speed of Light
The speed of light in a vacuum is about 3.0 x 108 ms-1.
Light travels much slower in transparent materials.
Example
• By applying the principle of reversibility of light, light travelling from point A to point B through any system can also travel from B to A along the same path in the reverse direction.
n 1
Sin i 1
Sin r
Sin i Sin r
i r
Answer
ACTIVITY
In groups, do the experiment according to the task given. Explain in detail.
Real Depth and Apparent Depth
water
Apparent Depth,h
Real Depth , H
image
Aplication