1. Topic 7 The Wave Model of Light
Newton believed that light could not bend around corners , it could only travel in a straight line.
Christiaan Huygens proposed that light traveled in waves not streams of particles as he noticed that light seemed to spread out as it passed through an opening.
He compared it to the movement of waves in water

2. The Wave Model Each wave has a crest and a trough.
Crest being the upper part of a wave.
Trough being the lowest part of the wave.
Each wave has a wavelength, an amplitude and a frequency, in hertz.
The wavelength is the distance between 2 crests or two troughs.
The amplitude indicates the energy of the wave.
The frequency is how often a crest passes a point in a second, called a cycle.

3. Lasers
According to the “wave model” an incandescent light bulb gives off many different colours. The waves are jumbled and may work against each other (and cancel each other out).
Incoherent light
Lasers emit waves with only one frequency or wavelength
Coherent light
Powerful and precise
See Fig 3.60A and 3.60B
See Fig 3.61A, 3.61B, 3.61C and 3.61D

4. Optics!
Optical fibre is designed to reflect light within the plactic tubing so that the energy can only escape at the ends.
Optical fibres are being used in the following areas:
Television
Telephone
Medicine

5. Topic 8 Electromagnetic spectrum

6. ROYGBIV Frequency and wavelength on Page 249

7. Types of electromagnetic radiation
Infrared Radiation: Thermal or heat radiation.
The radiation that is seen when thermal heat is transferred to and from an object within an environment.
Radio waves: sound waves.
Microwaves shortest of all radio waves. They need to be amplified then retransmitted to be heard.
Radio waves: longest of all radio waves. RADARSAT and LANDSAT are the most common uses of radiowaves. Refer to page 252.

8. Types of electromagnetic radiation
Ultraviolet radiation: a high energy radiation. Absorbed similarly to radiowaves.
X rays: electromagnetic radiation that is capable of penetrating through skin as it is more energetic than Ultraviolet rays
Gamma rays are the shortest and the most energetic of all the electromagnetic radiation.
Capable of destroying human cells, so it can be used as a cancer treatment.