1. 7. Rays and waves
7.01 light rays and waves

2. Rainbow

3. Characteristics of light
Light is a form of radiation
Light travels in straight lines
Light transfers energy
Light travels as waves
Light can travel through empty space (vacuum)
Speed of Light is km/sec

4. Light in Everyday Life Light is a form of energy, radiative energy
1 Watt = 1 Joule/sec
Light has color
A prism split light into a spectrum (rainbow of colors)
Light travels with a speed of c=300,000km/s

5. Properties of light
Dispersion of light: Splitting of white light into its constituent colours

6. Light Travels In Straight Line
Experiment
Experimental setup
light-travels-in-straight -line

7. No light is seen when one of the boards is displaced
That is when the slits are not in a straight line.
Conclusion : in a homogenous transparent medium, light travels in a straight line.
homogenous : having the same properties throughout

8. We represent the path of the light by a straight line called the light ray. The arrow indicates the direction of travel of the light.
Light from a point source spreads in all directions.

9. A light beam is a collection of light rays.

10. Luminous & non- luminous objects
Luminous objects– Objects that emit their own light.
eg- sun, lamps, lasers, glowing TV screens
Non-luminous objects- Object that do not emit their own light. They reflect light.
eg- moon,