Notes
VIDEO 1
 Light is defined as the electromagnetic radiation with wavelengths
between 380 and 750 nm which is visible to the human eye.
 We see objects around us because of light reflecting from them.
 Luminous objects generate their own light.
 Non-luminous are objects that can not generate their own light but instead
reflect the light from the luminous object from their surfaces. As a result of
reflection, we see objects around us.
 Ray of light is a straight line path along which light travels.
 Light emitted by luminous objects travels in all directions.
 Rays of light obeys laws of reflection
 Line perpendicular to the surface at the point of incidence is called the
normal.
 Angle of incidence is always equal to the angle of reflection.
 Angle of incidence is the angle made by the incident ray with normal.
 Angle of reflection is the angle made by the reflected ray with normal.
 The incident ray, reflected ray, and normal all lie in the same plane.
VIDEO 2
 The beam of light partially reflects, refract and absorb by the object.
 The light ray which is incident is reflected in such a way that the angle of
incidence and angle of reflection are equal.
 The incident ray, reflected ray, and normal all lie in the same plane.
 Refraction is the change in the direction of light as it passes across the
boundary separating two media caused by its change in speed.
 If the refractive medium is optically denser to incident medium, then the
refracted ray will bend towards the normal.
 Snell’s Law is the relation between the incident and refraction angles and
the refractive indices of the mediums.
 Refractive index of a medium is the extent to which the refractive medium
increases or decreases the speed of light.
 Mathematically it is the ratio of the speed of light in the incident medium
and the speed of light in the refractive medium.
 Denoted by n and the two numbers as the base of the two medium
 Read as, refractive index of medium 2 with respect to the incident medium
1.
 V1 and V2 is the speed of light in medium 1 and 2.
 Refractive index of a medium is the extent to which light changes its
direction in the refractive medium.
SNELL’S LAW OF REFRACTION
 Tells us the ratio of the sine of the angle of incidence to the sine of angle
of refraction is equal to the refractive index of the second medium with
respect to the first medium.
 Absolute refractive index is the refractive index of a medium with respect
to vacuum.
 C is the speed of light in the vacuum
VIDEO 3
 Refraction of light is the bending of light when it travels from one medium
to another.

The change in direction of light occurs because of the change in the
speed of light in that medium.
 When light enters another medium, there is a change in its speed. The
speed may either increase or decrease depending on the medium.
 Speed of light in a vacuum - 3 x 108 m/s
 Because of the change in speed the direction of light increases.
 Yes, it’s speed will change, however it does not bend. The refracted ray
propagates in the same direction as the incident ray.
 Air to glass - bends towards the normal
 Glass to air - bends away from normal
 Optically rarer to Optically denser medium it bends towards the normal.
 When the light travels from an optically denser medium to an optically
rarer medium it bends away from the normal.
 Optical medium is a medium which light can propagate.
 If the refractive medium is optically rarer compared to the incident medium
the speed of light in it will be greater.
 When the refractive medium is optically denser compared to the incident
medium the speed of light in it will be lesser.
 When a ray of light is travelling from an optically rarer to optically denser
medium, its speed will decrease and it will bend towards the normal.
 On the other hand, when a ray of light is travelling from an optically
denser medium to an optically rarer medium, it speed will increase and it
will bend away from the normal.
 The refraction of a light ray depends on the material medium on which
light is incident.
VIDEO 4
 Snell’s law tells us that the ratio of the sine of the angle of incidence to
the sine of angle of reflection is constant and is equal to the refractive
index of medium 2 with respect to medium 1. Equal to the ratio of speed
of light in medium 1 to the speed of light in medium 2. The same as the
ratio of absolute refractive index of medium 2 to the absolute refractive
index of medium 1.
VIDEO 5
 When a light beam is incident to the surface of the object a part of it could
be reflected, refracted (transmitted) or absorbed. It depends on the
material that the object is made of.
 If the object is opaque it will reflects most of the light.
 When the object is transparent it transmits or refracts most of the light.
 Refraction of light is the bending of light as it travels from one medium to
another.
 Obliquely means slant.
 Bending of light happens at the boundary of the two mediums air and
glass.
 The medium from where the light is incident is called the incident medium
and the medium where refraction occur is the refractive medium.
VIDEO 6
 Beam of light is not the same as ray of light. Ray of light is an idealization
of a beam.
 Ray of light as a narrow beam of light.
 Critical Angle