24 The Wave Nature of Light

•Light has a dual nature …of particle and of wave.•Huygen’s principle …Every point on a wave front can be considered as a source of tiny wavelets that spread out in the forward direction at the speed of the wave itself. The new wave front is the envelope of all the wavelets…that is, the tangent to all of them.•Diffraction is the bending of waves as they pass by an object or through a thin opening.•See diagrams page 724.

24-2 Huygen’s Principle and the Law of Refraction

• Wavelength depends on n…speed of a wave changes from medium to medium…frequency remains the same.

• ln = l/n pg 726• See highway mirage images pg 727

24-3 Interference –Young’s Double-Slit Experiment

• Thomas Young (1773-1829) obtained convincing evidence of the wave-nature of light by using a double-slit experiment. Pg 727

• Constructive interference is where 2 crests or troughs meet and destructive interference is where a crest and trough meet.

• This causes a light/dark/light pattern as light travels through a double slit…much like water waves.

• See page 729 Example 24-1 (See formulas)

24-4 The Visible Spectrum and Dispersion

• The intensity is the energy light carries per unit of time.

• The color of light is related to the frequency or wavelength.

• Dispersion is the splitting of light based upon differential refraction through a second medium.

HOMEWORK

• Page 752 pr#2-4, 13-15 due Wed. BOP