1. Light Energy
Chapter 5.4

2. Introduction to Light

3. Electromagnetic Spectrum
Energy released from the sun is called electromagnetic radiation
Most of the waves in the electromagnetic spectrum is invisible to us
The waves are all different types of light, the only difference is their wavelength and frequency

4. Visible spectrum
This spectrum is made up of different colours ROY G BIV
Each colour has waves of slightly different lengths
Red light has the longest wavelength and the lowest frequency
Violet has the shortest wavelength and the highest frequency

5. Why does the ball look yellow?
When sunlight hits the surface of the ball, it absorbs the all the energy from all parts of the spectrum EXCEPT YELLOW. Our eyes see only these REFLECTED colours and our brain recognises the ball as being yellow.

6. What happens to light energy?
When light hits a surface, it may be:
Reflected from the surface: that can be thought of as the light waves bouncing off the object it is hitting. White objects reflect ALL parts of the visible spectrum absorbing none.
Absorbed into the substance: all the light energy that hits the object is taken in and changed into other forms of energy. Black objects absorb all parts of the visible spectrum reflecting none.
Transmitted through the substance: Transparent or translucent objects will all light energy to pass through them

7. Luminous objects Objects that give out their own light
We get to see luminous objects because their light enters our eyes directly
Examples include: the sun, stars, glow-worms and fire-flies

8. Non-luminous objects Objects that do not give out their own light
We get to see non-luminous objects because light is reflected from them and into our eyes
Examples include: the moon, planets, trees and animals

9. Transparent objects
Almost all light is transmitted through the substance
A clear image can be seen through the substance
Eg: glass, shallow water

10. Translucent objects
Some light may be reflected, and light that passes through is scattered
An image seen through the substance is fuzzy
Eg: plastic bags, frosted glass, tissue paper

11. Opaque objects
Light is either reflected from or absorbed into the substance
No light is transmitted
No image can be seen through the substance
Eg: brick, wood, football, tree