This document discusses the concept of refraction of light. It defines refraction as the change in direction of light when passing from one medium to another. It explains that when light travels from a less dense to a more dense medium, it bends towards the normal, and when traveling from more dense to less dense, it bends away from the normal. It also discusses total internal reflection, which occurs when light travels from a denser to less dense medium at an angle greater than the critical angle, causing the light to reflect internally rather than refracting.

1. WELCOME

2. KERALA UNIVERSITY COLLEGE
OF TEACHER
EDUCATION,KOLLAM

3. Refraction of Light
LIGHT

4. LIGHT
•What is Refraction?
•What is Optical Density?
•The Laws of Refraction
•The Refractive index
•Angle of Incidence / Refraction
•Total Internal Reflection

5. LIGHT
Refraction is the change in
direction of light when it passes
from one medium to another.

6. LIGHT
If light ray enters another medium perpendicular to
boundary, the ray does not bend.

7. LIGHT
When the light ray travels
from air to water, the
refracted ray bends
towards the normal.
i
r
air
water
Incident ray
Refracted ray
normal
i – angle of incidence
r– angle of refraction

8. LIGHT
When the light ray travels
from water to air, the
refracted ray bends away
from the normal.
i
r
air
water
Incident ray
Refracted ray
normal
i – angle of incidence
r– angle of refraction

9. LIGHT
During refraction, light
bends first on passing
from air to glass and
again on passing from
the glass to the air.

10. LIGHT
During refraction, light
bends first on passing
from air to glass and
again on passing from
the glass to the air.
i
r
Incident ray
Emergent ray
Refracted ray
Reflected ray
air
air
glass

11. LIGHT
Light slows down when it enters an optically denser
medium. The refracted ray bends towards the normal
when the second medium is optically more dense than
the first.
i
r
air
water
Incident ray
Refracted ray
normal

12. LIGHT
Light speeds up when it enters an optically less dense
medium. The refracted ray bends away from the normal
when the second medium is optically less dense than
the first.
air
water i
r
Incident ray
Refracted ray
normal

13. LIGHT
Among the 3 transparent mediums (air, water and
glass), glass has the highest optical density.
air
water
i1
r1
Incident ray
Refracted ray
glass
i2
r2
Refracted ray
air
water
i1
r1
Incident ray
glass
i2
r2
Refracted ray
Refracted ray

14. LIGHT
Take a look at this...

15. LIGHT
The critical angle is the angle of incidence in the
optically denser medium for which the angle of
refraction is 90o
.
When i = critical angle,c
r = 90o
.

16. LIGHT
This is called TOTAL INTERNAL REFLECTION.
When i > critical angle, the ray gets reflected internally.

17. LIGHT
For TOTAL INTERNAL REFLECTION to take place:
The light ray must travel from an optically denser
medium towards a less dense one.
The angle of incidence must be
greater than the critical angle.
Direction of light path
i

18. LIGHT
How do we calculate the critical angle?
We know that r = 90o
…

19. LIGHT
Total Internal Reflection in Prisms

20. LIGHT
Total Internal Reflection in Prisms

21. LIGHT
Fibre Optics

22. THANKYOU