1. Light

2. Where does light come from?
Without light energy you could not see anything!!!!!!!!
Light energy
* Gives things colors
* Helps plants to grow
* Can power solar batteries to make electricity
* Used in lasers.
Our major light source:
the Sun

3. Light sources
Natural vs Man-made (artificial)

4. Incandescence
Fluorescence
The production of light energy when an object is heated to a high temperature
Production of visible light by an object that has absorbed invisible radiation; conversion of UV light  Visible light

5. Bioluminescence
Chemilumninescence
Production of light from a chemical reaction within an organism (scare predators, lure prey, attract mates)
Production of light from a reaction between two chemicals

6. Part 1: Properties of light?
Light is a kind of energy.
Light energy travels through space as an electromagnetic wave.

7. Properties of Waves
Wavelength: (distance in meters from one point to another similar point.
Frequency: How many waves can occur within a given period of time.
Different Light has a certain amount of energy associated with it.

8. Electromagnetic Spectrum
Short wavelength – High Frequency
Long wavelength – Low Frequency

9. Visible Light – Light that can be seen with the human eye

10. Prisms bend or refract light!
White Light
White light is not a single color; it is made up of a mixture of the seven colours of the rainbow.
We can demonstrate this by splitting white light with a prism. Try now with defraction grading.
This is how rainbows are formed: sunlight is “split up” by raindrops.
Prisms bend or refract light!

11. Light waves travel in straight lines:
Chalk Demo as proof
Laser

12. Light travels VERY FAST – around 300,000 kilometers per second.
At this speed it can go around the world 8 times in one second.

13. Light travels much faster than sound. For example:
Thunder and lightning start at the same time, but we will see the lightning first.
2) When a starting pistol is fired we see the blast first and then hear the bang.

14. We see things because they reflect light into our eyes:
Homework

15. Are these light sources?
moon
mirror
water
These items are not light sources, instead they are reflecting light from other sources.

16. Luminous and non-luminous objects
A luminous object is one that produces light.
A non-luminous object is one that reflects light.
Luminous objects
Non-luminous

17. Shadows
Shadows are places where the straight lines of light are “blocked”:
Rays of light

18. How does light form shadows?
source
light
source
Light rays travel in straight lines, radiating out from the light source.
If rays are blocked by an opaque object a shadow forms where the light cannot reach.
If the light source is moved closer to the object, more light is blocked and a larger shadow is formed.