Let There Be Light Last chapters of the

Let There Be Light Last chapters of the semester

This Week • Quiz • Begin our study of electromagnetic waves. • No quiz on Friday • Next week, more of the same.

For Exam #4 • Section 20. 5 – Alternating Current • Sections 23. 1 -4 • We will start today with Chapter 24 – Electromagnetic Waves and work on the new unit. • There will be no problem solving session on Monday. Perhaps on Wednesday (if there is interest). I would review AC problems.

VERY TIGHT SCHEDULE Monday November December Wednesday Friday 15 – Short Review & Unit 15 AC 17 – EXAM #3 Unit 15 AC 19 Unit 15 AC 22 Unit 16 Optics 24 QUIZ Unit 16 Optics 26 Holiday 29 Unit 17 -18 Optics 1 Unit 18 Optics 3 QUIZ Unit 18 Optics 6 LAST DAY EXAM #4 Saturday 11 FINAL 7: 00 AM HPA 119

Assignment • Read Chapter 24, sections 1 -4, 6, 7 – WA will appear shortly • You should also start reading chapters 25, 26 and 27. We will only cover certain topics in these chapters but some of the home works will come from other sections.

Light • James Clerk Maxwell (1831 - 1879) was a genius who studied the properties of Electricity and Magnetism. He took a mathematical approach. He published his first scientific paper when he was 15 years old. • The four mathematical equations Maxwell produced are ranked with Sir Isaac Newton's laws of motion and Albert Einstein's theory of relativity as the most fundamental contributions to (“classical” )physics. • Maxwell’s equations predicted that the electric field and the magnetic field could propagate through empty space. • The calculated velocity of these waves turned out to match the speed of light to a very close precision. • It was later demonstrated that these waves were, in fact, light waves.

Propagation of Light • The electric and magnetic fields are predicted (and verified) to be perpendicular to each other. • The propagation velocity is found to be “c”, the speed of light in a vacuum. – c=3 x 108 m/sec. • Maxwell calculated that the speed of light in a vacuum to be

Propagation of Light l • Since the E and B fields (vectors) are perpendicular to the direction of propagation, the wave is said to be TANSVERSE. • Because of this fact, the light wave can be “polarized” • The wavelength l of the wave is shown in the diagram. • The product of the frequency and the wavelength is c so we see that light can come in different wavelengths (c is a constant)