This document discusses key concepts related to the refraction of light, including: - Refraction occurs when light passes from one medium to another, changing direction as it enters the new medium. The degree of bending depends on the optical density of the materials. - Two laws govern refraction: Snell's law states that the ratio of sines of the angles of incidence and refraction is a constant; and the law of refraction states that the incident ray, refracted ray, and normal all lie in the same plane. - The refractive index is a measure of how much light bends when entering a material, and depends on the material's optical density - the higher the density, the greater the refractive index

2. CONTENTS
Refraction
Optical Density
The Laws of Refraction
Refractive index
Total Internal Reflection

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

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

5. When the light
ray travels from
air to water, the
refracted ray
bends towards
the normal.
• i – angle of
incidence

6. • When the light ray
travels from water
to air, the
refracted ray
bends away from
the normal.
• i- angle of
incidence
• r- angle of

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

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

9. Optical density
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.

10. 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.

11. Among the 3 transparent mediums
(air, water and glass), glass has the
highest optical density.

12. LAWS OF REFRACTION
The incident ray, the refracted ray and
the normal at the point of incidence all
lie in the same plane.

13. For two given media,
the ratio sin i ÷ sin r
is a constant, where i
is the angle of
incidence and r is
the angle of
refraction light.
Refractive sin i
Index,n sin r

14. Refractive index
The higher the optical density, the
greater the refractive index. The greater the
refractive index, the greater the bending of
light towards the normal.

15. n = sin i /sin r n = sin r /sin i
When light travels from
a less dense medium to
a denser medium…
When light travels from
a denser medium to a
less dense medium…

16. Other ways of calculating the
refractive index…
Refractive index,
n = real depth/apparent
depth
Refractive index,n=Speed of light in vacuum or air /Speed of
light in medium = c /v

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

18. TOTAL Internal reflection
When i > critical angle, the ray gets
reflected internally. This is called TOTAL
INTERNAL REFLECTION .

19. 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.
i

20. We know that
when light travels
from a less dense
medium to a denser
medium.
We know that
when light travels
from a denser
medium to a less
dense medium
Refractive sin r
Index, n sin i
Refractive sin i
Index, n sin r