PHYS 1750: SELECTED TOPICS in PHYSICS
LECTURE 36. Electromagnetic Waves
23.1. | Maxwell's Equations Without Charges | |
1. | ∑ ΔA*E⊥ = 0; sum over surface elements of a volume | |
2. | ∑ ΔA*B⊥ = 0; sum over surface elements of a volume | |
3. | ∑ Δl*E|| = − ΔΦB / Δt; sum over line elements of a loop | |
4. | ∑ Δl*B|| = μoεo ΔΦE / Δt: sum over line elements of a loop | |
23.1. | Wave Solution | |
1. | Changing E creates/destroys B | |
2. | Changing B creates/destroys E | |
23.2. | Waves from an Antenna | |
1. | Changing electric dipole produces E | |
2. | Alternating current produces B | |
23.1-2. | Properties of EM Waves | |
1. | Speed of light c =1/sqrt[ μoεo] = 2.99792×108 m/s | |
2. | E/B = c | |
3. | Transverse wave: polarization | |
23.3-4. | The Spectrum of EM Waves | |
1. | Wavelength and frequency | |
2. | Intensity (energy content) proportional to amplitude squared | |
Power/area = Emax2/ 2μoc | ||
3. | Radio, microwave, infrared, visible, ultraviolet, X-ray, γ-ray |