The Wave Nature of Light

1. The Wave Nature of Light Unit 4

2. Wave Theory Waves are a travelling disturbance. They carry energy from one location to another • Mechanical Waves • governed by Netwon’s laws • require a physical medium • ex. water, sound, air columns in instrument • Electromagnetic Waves • can travel through a vacuum (space) at speed of light • ex. visible light, infrared, UV • Matter waves • model that amalgamates the particle and wave theories of energy and matter • e- p+ n0 all can behave like waves

3. Two general types of waves • Transverse • particle motion is perpendicular to direction of wave velocity • Ex. light • Longitudinal • parallel • Ex. sound • SHM: oscillating source, repetitive motion • The relative position of two particles on the wave is called phase

4. Reminder of Terms • Period (T) • The amount of time (t) it takes a wave to complete one cycle. Units: (s) • T = t/N N = # of cycles • Frequency (f) • The # of these cycles that can occur in one second. Units: Hz (cycles/s) f = N/t

5. Reminder of Terms • Wavelength (λ) • The length of one complete cycle. Units: (m) • Amplitude • The maximum disturbance of the wave from its zero point. (+ and - )

6. Phase Shift • See Pg 490 in text

7. Properties of Electromagnetic Waves • Alternating oscillating electric and magnetic fields • Fields are perpendicular to each other • Vibration of E and M fields is perpendicular to the direction of the wave’s motion and .’. they are transverse waves • E and M fields vary sinusoidally in phase with each other • Travel at c in a vacuum. In other mediums, travel at different speeds, which causes refraction.

8. Universal Wave Equationv = λf

9. Electromagnetic Spectrum

10. Electromagnetic waves travel through a vacuum at the speed of light, c.3.0 x 108 m/s