Science 8: Unit C – Light and Optics

1. Science 8: Unit C – Light and Optics Topic 7: The Wave Model of Light

2. Wave Model of Light • Created by Christian Huygens in the 1600s. • Light travels as waves of energy, not particles of matter. • Light travels in transverse waves (eg. waves move up and down).

3. Characteristics of Waves • The highest part of the wave is called the crest, the lowest part is the trough. • One crest and one trough together make up one wavelength measured in m. • The color of light depends on the wavelength of the wave. • The resting point of the wave (middle ground) is called the equilibrium.

4. Characteristics of Waves Cont’d • The amplitude of a wave is the distance from the equilibrium to the crest/trough. (it’s measured in m) • The greater the amplitude the more intense the wave (brighter the light when it comes to light waves)

5. Characteristics of Waves Cont’d • Frequency is the number of wavelengths completed per second (or that move past a certain part) • The unit for frequency is the hertz (Hz) • To calculate the speed of a wave: • Speed of wave= frequency of wave X wavelength of wave

6. Frequency and Color • The higher the frequency of a light wave, the smaller its wavelength and the more energy it contains. • Eg1. Because red light is longer it is the first and last color of light to reach over the horizon during sun-up and sundown. • Eg2. DVDs rely on a red laser to read information. The new Blu-Rays use blue lasers which can read more information because of their smaller wavelengths.

7. Coherent and Incoherent Light • White light contains light of many different wavelengths which can overlap and cancel each others’ colors. This is called incoherent light. • Coherent light is light of all the same wavelength which amplifies the crests and troughs making the light more intense and of the same color. This is the kind of light used in lasers which have a wide range of applications.

8. Green Laser