1. Refraction of light

2. Cause of Refraction In different mediums,
- Optical density is different,
-so speed of light is different
Greater optical density, lesser speed of light

3. Refraction from air(rarer) to glass (denser) medium

4. Refraction from denser to rarer medium

5. Refraction at normal incidence

7. Laws of Refraction
The incident ray, the refracted ray and the normal at the point of incidence, all lie in the same plane.

8. Refractive Index
For two particular media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant(Snell`s law).

9. Speed and Refractive Index
Speed of light in vacuum = 3 x 108 ms-1
Light is found to move slower in optically denser mediums. (eg. glass and water)

10. Properties affected due to refraction
Property
Air to Glass
Glass to Air
Frequency
Remains constant
Speed
Decreases
Increases
Wavelength
Direction
Towards normal
Away from normal

11. Factors affecting RI Nature of material Wavelength (colour) of light
Greater the speed, lesser the RI
Wavelength (colour) of light
Greater the wavelength, lesser the RI
Temperature of material
Greater the temperature, lesser the RI

12. Lateral Displacement
The perpendicular distance between the path of incident ray and emergent ray is called lateral displacement.
The perpendicular distance between the path of incident ray and emergent ray is called lateral displacement.

13. Factors affecting Lateral displacement
1. The thickness of the glass
2. The angle of incidence
3. The refractive index of glass
4. Wavelength/frequency of incident ray

14. Principle Of Reversibility
The principle of reversibility of light states that the path of a ray of light is reversible.
According to this principle , if a ray of light travels from A to B along a certain path, it will follow exactly the same path, while travelling from B to A

15. or amg represents refractive index of glass with respect to air then
Similarly if refraction occurs from denser to rarer medium or
The above expression is an important result of the principle of reversibility of light which states that when a ray of light after suffering a large number of reflections and refractions has its final path reversed, it travels back along the same path in the opposite direction as shown above.

16. Real and Apparent Depth
Consider a ray of light incident on XY, normally along OA, it passes straight along OAAl. Consider another ray from O (the object) incident at an angle i on XY, along OB. This ray gets refracted and passes along BC. On producing this ray BC backwards, it appears to come from the point I and hence AI represents the apparent depth, which is less than the real depth AO.
When angles are small, B lies close to A such that
OB ~ OA
IB ~ AI
∟AOB = ∟OBN= i ( alternating angles) B

17. Apparent position and twinkling of stars
The atmosphere consists of a number of parallel layers of different densities. Varying temperature and pressure account for the different densities. As the rays enter in layers of increasing densities they are being continuously refracted . In the process, the rays follow a curved path and reach the observer. But due to the wind and convection currents, the density of the layers go on changing. Therefore, after very short intervals of time, the position of the image of the star keeps changing ,and produces the twinkling effect

18. Apparent sunrise/sunset
Due to atmospheric refraction, sunrise occurs shortly before the sun crosses above the horizon. Light from the sun is bent, or refracted, as it enters earth's atmosphere. This effect causes the apparent sunrise to be earlier than the actual sunrise. Similarly, apparent sunset occurs slightly later than actual sunset. The sunrise and sunset times reported in our calculator have been corrected for the approximate effects of atmospheric refraction. However, it should be noted that due to changes in air pressure, relative humidity, and other quantities, we cannot predict the exact effects of atmospheric refraction on sunrise and sunset time. Also note that this possible error increases with higher (closer to the poles) latitudes.

19. Spear Fishing
Spear fishermen use a strange trick to catch their prey. They aim at a point slightly below where the fish seems to be. The reason is that light changes direction when it moves from one transparent substance, such as water, to another of different density, such as air. This change of direction is called REFRACTION.

20. Bending of stick in water
A stick immersed in water
appears bent and short at the
surface of water when viewed
obliquely from above. This is
because the rays of light travel
from water to air and bend
away from the normal at the
surface

21. A coin appears raised in water
Place a coin A at the bottom of an
empty vessel. The position of the
eye is so adjusted that the coin
cannot be seen. Now slowly fill
the vessel with water and maintain
a steady gaze at the coin. The coin
gradually begins to appear. Thus,
B is the raised , apparent position
of the coin A due to refraction of
light B A

22. Multiple images in a Thick Glass Plane Mirror

23. Total Internal Reflection
As the angle of incidence increases,
the angle of refraction increases

25. Critical Angle
Critical angle is the angle at which the refracted ray is at 90o

27. Conditions for TIR
The ray must travel from denser medium to rarer medium. The angle of incidence i must be greater than critical angle C

28. Distinction between total reflection and reflection from a plane mirror
Total internal reflection
It takes place when light passes from a denser medium to a rare medium when angle of incidence is greater than the critical angle
The entire light is reflected
There is no loss of energy
The image is much brighter and the brightness is permanent
Reflection from a plane mirror
It takes place when light is incident on a plane mirror from any medium at any angle of incidence
Only part of light is reflected while rest is refracted and absorbed.
The energy of reflected ray is less than that of the incident ray
The image is less bright and the brightness gradually decreases.

29. Total internal reflection in a Prism
This action of prism is used in a periscope
A periscope may be used by people (i)  in a submarine to see above the sea surface (ii)  to see over the heads of people in a crowd.

30. Deviation through 180 degree
This action of prism is used in binocular

31. Erecting Prism
This action of prism is used in a slide projector

32. Deviation through 60 degree by an Equilateral Prism

33. Total internal reflection and refraction of light through
30◦ ,90◦,60◦Prism
No total internal reflection
Total internal reflection takes place

34. Consequences of total internal reflection
TIR in Diamonds
Sparkling is due to:
Cut of diamond faces
High index of refraction which means a very small critical angle (n = 2.42, C = 24.4°)
Incident rays can undergo multiple TIR inside a diamond before exiting the top of the diamond.

35. REFRACTION THROUGH A PRISM

36. PRISM A prism is a transparent ref
A prism is a transparent refracting medium
Bounded by two plane surfaces making an angle with each other.
medium

37. PRINCIPAL SECTION OF THE PRISM
The section of the
prism
prism perpendicular to
the refracting edge
is called the principal
section of prism.
the
refracting edge
section of
prism.
REFRCTING ANGLE
REFRACTING SURFACE
REFRACTING SURFACE
BASE C B

38. DEVIATION BY A PRISM

39. Dependence of angle of deviation on the angle of incidence i-ᵟ curve
minimum deviation.
When the angle of incidence
is increased further, the angle
of deviation now starts
increasing.

40. Relation between angle of incidence, angle of prism, angle of deviation and angle of emergence
A + δ = i + e 

41. Factors affecting the angle of deviation
The angle of incidence
The material of the prism
The angle of the prism
The colour or wavelength of light
used.