ELECtromagnetic waves Light etc. PHY 2054 Spring 2011 April 13, 2011
Title • Today we start the study of electromagnetic waves and LIGHT as in “let there be”. • This will lead to a discussion of • Polarization • Mirrors • Lenses • Perhaps interference and diffraction • There are available experiments for each of these. Not sure how far we will get but we will get there quickly!
WHERE IS THE FINAL EXAM??
What’s on Exam #3? • Questions! • 5 Multiple choice questions • Three problems covering • Magnetism • Induction • AC Circuits
A sound wave • is a transverse wave • is a longitudinal wave • travels at the speed of light • has a color spectrum
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.
Maxwell’s Equations Gauss’s Law No Mag Poles!! Faraday’s Law Ampere’s Law Displacement Current
Which way is the electric field at P pointing? A Left B Right C Up D Down E In/Out P
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=3x108 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)
Polarization Polarized Unpolarized
Today’s Experiment • Polarized Light • Read the material at the beginning of the experiment that we haven’t covered • Don’t read what we covered today • Do the experiment • Next time the math!
Get a Blue Box and get to work!!! OPTICS STUFF