The document explains the nature of light, including its properties, types of luminous and non-luminous objects, and concepts like reflection and refraction. It outlines the laws governing these phenomena, defines the refractive index, and describes the behavior of light when passing through different lenses. Additionally, it details how images are formed by lenses, distinguishing between real, inverted, and diminished images.

1. LIGHT

2. What is
Light?
Light is the part of the EM spectrum which
we can see.
Light travels in straight lines called rays.
A bundle of rays is known as a beam of light.
A ray A parallel
beam
A
divergent
beam
A
convergent
beam

3. Luminous and Non-
Luminous
Luminous objects are those that give off light
on its own.
Example: Light bulb, SunExample: Light bulb, Sun
Non-luminous objects are objects that do not
give off light on its own.
Example: table, board, MoonExample: table, board, Moon

4. Reflection
Reflection is the bouncing of light rays off
a surface.
We are able to see non-luminous objects
as light is reflected off them.

5. Laws of Reflection
The incident ray, the reflected ray and the normal all lie on
the same plane.
The angle of incidence is equal to the angle of reflection.

6. Reflection for Different
Surfaces
Regular reflection
•On smooth
surfaces
Diffused reflection
•On rough
surfaces

7. Properties of Image Formed by Plane
Mirror
Same size as the object
Laterally inverted (left-to-right inversion)
Upright
Virtual (image cannot be caught on a screen)
Object distance is equal to image distance

8. Ray Diagram for Reflection
Object, O
observer

9. Image, I
observer
Object, O

10. observer
Ray Diagram (Extended object)

11. observer

12. Refractio
n
 Refraction is the bending of a wave when it enters a medium where its speed
is different. The refraction of light when it passes from a fast medium to a
slow medium bends the light ray toward the normal to the boundary between
the two media.
 The amount of bending depends on the indices of refraction of the two media and is
described quantitatively by Snell's Law.

13. Laws of Refraction
first law of reflectionfirst law of reflection
The incident ray, the refracted ray and the normal all lie in the same
plane.
Second law of reflectionSecond law of reflection
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.

14. Refractive
Index
 The ratio of the velocity of light in a vacuum to its velocity in a specified medium. Known
as the refractive index
r
i
n
sin
sin
=
Angle of incidence
Angle of refraction
(Snell’s Law)

15. Speed and Refractive
Index
Speed of light in vacuum = 3 x 108
ms-1
Light is found to move slower in optically denser
mediums. (e.g. glass and water)
Material n Material n
Vacuum 1.000 Ethyl alcohol 1.362
Air 1.000277 Glycerin 1.473
Water 4/3 Ice 1.31
Carbon disulfide 1.63 Polystyrene 1.59
Methylene
iodide
1.74 Crown glass 1.50-1.62
Diamond 2.417 Flint glass 1.57-1.75

16. There are two different types of
lenses.
Convex
Lens
Concave
Lens
SPHERICAL LENS

17. Start with the convex lens.
Convex lenses are also known as
converging lenses
Concave lenses are also known as
diverging lenses
Convex
lenses
Concave
lensesAND

18. Principal focus
Incident rays of light are parallel
Convex lenses

19. Incident rays are parallel
Rays leaving the lens are diverging
Concavelenses

20. Forming Images
The rays of light from the car are converged by the lens, to form an image on
the screen.
The image is inverted (upside down)
and real (the rays of light pass through the lens and an image is
formed on the screen)
and diminished (smaller than the object).
Screen

21. Film/screen
Image: Real, Inverted and
diminished
Object
In a camera the image is
smaller than the object we
say the image is diminished
Camera