This document discusses refraction of light, including the definition of refraction, the difference between refraction and reflection, how to label a refraction diagram, the index of refraction, and how light behaves when passing between media of different densities. Specifically, it explains that when light passes from a less dense to more dense medium it bends toward the normal, and from a more dense to less dense medium it bends away from the normal, up until the critical angle where total internal reflection occurs. Diagrams are provided to illustrate examples of light passing between air and water.

1. REFRACTION OF LIGHT
Done by : SALAH A. AL SARY
Grade : Nine
Subject : Physics

2. Contents :
1.Definition
2.Difference between RefRaction and
refLection of Light
3.Labeling Refraction Diagram
4.Index of refraction
5.Path of Light when it:
Falls perpendicularly on the surface of
separation
Passes from less to more dense medium
Passes from more dense to less dense
medium

3. RefRaction of Light

4. What is RefLection of Light?
 Reflection is when light bounces off an object. If
the surface is smooth and shiny, like glass, water
or polished metal, the light will reflect at the
same angle as it hit the surface.

5. What is Refraction of Light?
 Refraction is when the speed and direction
of light changes, as light moves from one
transparent medium to another.

6. RefRaction Vs RefLection

7. Refraction Diagram
Incident ray : IO
Refracted Ray : OR
Normal : NN’
Surface of Separation
1. Incident angle ( i) :
angle between incident ray and normal
2.Refracted Angle ( r ) :
Angle between the refract ray and normal
3.Angle of Deviation ( D ) :
angle between the Prolongation of the incident ray and Refracted Ray
I
O
R
I’
‘

8. Index of refraction of a
medium
 Ratio of the speed of light in vacuum to the speed of light in
the medium ( speed of light vacuum ≈ speed of light in air).

9. Examples :

11. When Light Falls Perpendicularly
on the surface of separation :
 When a ray of light is incident perpendicularly on
the interface between two transparent media, it enters the
new medium without Deviation .
 Incident angle = 0ᵒ
 Refracted angle = 0ᵒ
 Deviated angle = 0ᵒ

12. Passage of light from less to
more dense medium :
When the light is passing from air (less dense)
into water (more dense), it is bent towards the
normal.
i > r
D = i – r

13. Example :
 i= 60ᵒ
r= 40ᵒ
D = 60 -ᵒ 40 =ᵒ 20ᵒ
Air
water

14. Passage of light from more to
less dense medium :
 When light passes from a more dense to a less dense
substance, (for example passing from water into air),
the light is refracted (or bent) away from the normal.
In this case we must take in consideration the
LIMITING ANGLE il .

15. Limiting angle il ( Critical angle)
The smallest angle of incidence at which a light ray
passing from one medium to another less refractive
medium can be totally reflected from the boundary
between the two.
 For the water-air boundary, the critical angle is 48.6-degrees.
 For the crown glass-water boundary, the critical angle is
61.0-degrees.

16. Cases of refraction :when light
passes from water to Air :
For the water-air boundary, the critical angle is 48.6-
degrees
Case 1 : i = 40ᵒ , il = 48.6ᵒ ( i < il )
The light is refracted (or bent) away from the normal.
D = r – i
D = 60ᵒ – 40ᵒ = 20ᵒ

17. Cases of refraction :when light
passes from water to Air :
Case 2 : i = 48.6ᵒ , il = 48.6 ᵒ ( i = il )
The ray grazes the surface of separation .
r = 90ᵒ
D = r – i
D = 90 - 48.6 = 41.4ᵒ ᵒ ᵒ

18. Cases of refraction :when light
passes from water to Air :
Case 3 : i = 60ᵒ , il = 48.6 ᵒ ( i > il )
The light undergoes TOTAL INTERNAL
REFLECTION .
i= r = 60ᵒ

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20. #Thank_YOU