Wave Nature of Light

• Speed of light: How Rømer measured it, Value in vacuo, c = 3.00 10⁸ m/s.
• Huygens' construction: General idea; how it is used to discuss interference and diffraction.
• Interference: General concept, constructive and destructive interference. Concepts of path difference, phase difference, and coherence.
• Interference with 2 slits: Why we wouldn't see interference with light coming from two different sources, and what we need to actually see an interference pattern; For two slits, maxima of light intensity occur at angles given by

d sin = n,   where   n = 0, 1, 2, 3, ...

• Interference with a diffraction grating: Maxima at the same location as with two slits, but the lines are much narrower; Can be used to separate light of different wavelengths and produce spectra.
• Diffraction from one slit: The angles at which minima of intensity occur are found using

D sin = m,   where   m = 1, 2, 3, ...

• Interference with a thin film: General idea is interference between light reflected at the surface and light that is reflected on the other side of the film after being refracted. When light meets the surface perpendicularly, constructive interference if the path difference 2d = n, unless the phase changes at one of the reflections, in which case one adds (1/2). Consequence, the colors on a thin oil film or soap bubble.
• The nature of light: Why one might think that light is made of particles; What is the main evidence for the fact that light is made of waves? Visible light has wavelength approximately between 450 and 700 nm.

Other Wave Phenomena with Light

• Dispersion: The index of refraction of a material usually depends on wavelength, and is larger for smaller wavelengths; Rays of light with smaller wavelengths are usually more deflected when refraction occurs; Therefore a prism separates light of different colors and produces spectra; Also, the focal length of a lens depends on wavelength.
• Polarization: Polarized light is light in which the electric (or magnetic) field oscillates preferentially in one of the directions that are perpendicular to the direction of propagation; The degree of polarization can range from not polarized to totally polarized.
• Polarizers: Light from many ordinary sources (such as regular light bulbs) is not polarized, but it can be polarized using a polaroid filter [reflection also partially polarizes light]; For initially unpolarized light, I = I₀/2; For totally polarized light, I = I₀ cos².
• The nature of light: What polarization tells us about it, longitudinal vs transverse waves.