Physics (university) · Part 09
Induction, light and optics
How changing magnetic fields make voltage, how light behaves as a wave and as rays.
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- Magnetic fluxHow much magnetic field passes through a surface, flux = B A cos theta. The unit is the weber.
- Faraday's lawA changing magnetic flux creates a voltage (emf) in a loop: emf = N x change in flux / change in time.
- Lenz's lawThe induced current flows in the direction that opposes the change in flux that made it.
- InductanceA coil's resistance to changing current. The voltage across it is L x change in I / change in t. It stores energy 1/2 L I squared.
- TransformerTwo coils on one iron core change AC voltage. The ratio of voltages equals the ratio of turns.
- Electromagnetic waveA wave of oscillating electric and magnetic fields that travels through empty space at c = 3.00e8 m/s.
- Electromagnetic spectrumThe family of EM waves ordered by frequency: radio, microwaves, infrared, visible, ultraviolet, X-rays, gamma rays.
- Snell's lawWhen light crosses between materials its direction bends: n1 sin theta1 = n2 sin theta2.
- Total internal reflectionLight going from a dense to a less dense material reflects completely beyond the critical angle, sin theta c = n2/n1.
- Thin lens equationLenses form images with 1/f = 1/object distance + 1/image distance.
- Double-slit interferenceLight through two narrow slits makes bright and dark fringes. Fringe spacing is y = lambda L / d.