Notes for 8th standard light chapter for the students.

1. Light

2. Introduction to Light
Light is the energy that enables us to see.
Light is emitted from a source such as the
Sun.
The word usually refers to visible light,
which is visible to the human eye and is
responsible for the sense of sight.

3. How do we see objects?
Our eyes alone do not
allow us to see.
 Light from a source falls
on an object and then
bounces off onto our eyes
and that is
how we perceive it.

4. Reflection
Light gets reflected off surfaces.
 Any surface that is really well-
polished or shiny acts as a
mirror.
The phenomenon of light
bouncing off surfaces is
called reflection.

5. Laws of Reflection
The ray of light that strikes a reflecting surface is called
the incident ray, and the ray that gets reflected back is
called the reflected ray.
The imaginary line that is perpendicular to the
reflecting surface is called the normal.
The angle of incidence ∠i is the angle between the
incident ray and the normal.
 The angle of reflection ∠r is the angle between the
reflected ray and the normal.

6. Laws of Reflection:
 Angle of incidence ∠i is always equal
to the Angle of reflection ∠r (∠i=∠r).
The angle of incidence, the angle of
reflection and the normal all lie
on the same plane.

7. Ray Diagram
The path taken by a narrow beam of
light is depicted as a ray diagram.

8. Regular Reflection
Reflection from a smooth surface like a
mirror that follows the laws of reflection is
called a regular reflection.

9. Diffused Reflection
Reflection over a surface that has irregularities
where it does not follow the laws of reflection is
called an irregular or diffused reflection.

10. Image formation in a plane
mirror
The image formed by a plane mirror
is always virtual, erect, and the
object and image are equidistant
from the mirror.
The image formed in a plane mirror
undergoes lateral inversion.

12. Multiple reflections
Two mirrors inclined to each other
give multiple images due to
multiple reflections.
When an object is kept between
two parallel plane mirrors, infinite
images are formed.

14. Calculating the total number
of images
The number of images formed by
plane mirrors is given by

15. Dispersion of light
The splitting of light into
its component colours is
called dispersion.
Example: Rainbow

17. Thank
You