Light 12346886253638383636363939383737377383939393

Notes

1. CLASS-10th
L1

2. Mysteries of light
The Dual Nature of Light: Photon & Wave theory
Reflection of Light: Laws
Reflection through Plane Mirror
Reflection through Spherical Mirrors
Rules of Image formation
Use of Spherical mirrors

3. JOSH METER

4. Light

5. Light is a form of energy which gives
sensation of vision.
Light itself is not visible otherwise
Universe would not be black.
Light is a Non-mechanical transverse
wave, that is why it travels in vacuum.

6. Optics is study of light.
There are two branches of optics:
Ray optics: Particle nature of light
Wave optics: Wave nature of light

7. Light also has the property of a particle.
The intensity of the light varies depending
on the number of particles. Bright light has
many particles while dark light has fewer
particles. These particles of light are called
“photons”.
Light travels at a speed of about 300,000
kilometers per second (c = 3 x 10^8 m/s).

8. When in a vacuum such as outer space
where no matter is present, light travels
straightforward, this is called Rectilinear
motion of light.
Several photons in a single line constitute a
light ray.
Several light rays constitute a beam of
light.

9. How do we see things?

10. The laws of reflection determine the reflection of incident light
rays on reflecting surfaces, like mirrors, smooth metal surface,
and clear water.
The Laws of reflection states that
The incident ray, the reflected ray and Normal all lie in the
same plane.
The Angle of incidence (i) = The angle of reflection (r)

13. Find the angle of reflection (r) through second mirror.

15. i. Concave mirror

16. ii. Convex mirror

17. Principal axis - A line joining the center of curvature and
pole is called principal axis.
Principal Focus - A point on the principal axis of a spherical
mirror where the rays of light parallel to the principal axis
meet or appear to meet after reflection is called principal
focus it is denoted by F.

18. Focal length - The distance between the pole and principal
focus of a spherical mirror is called focal length.
Optical center - It is a point on the principal axis of the lens
such that a ray passing through goes undeviated.

19. 1. A ray parallel to principal axis will pass through focus
after reflection.

20. 2. A ray passing through the principal focus will become
parallel to principal axis after reflection.

21. 3. A ray passing through center of curvature will follow the
same path back after reflection.

22. 4. Ray incident at pole is reflected back making same angle
with principal axis.

23. Concave mirror

24. Convex mirror