Is that a Mirage… or am I just seeing things?

An introduction to Physical Optics

Light - Introduction to Physical Optics

• Reflection, Refraction, Snell’s Law, Dispersion and the Wave-Particle Debate (Chp 33)

• Polarization (Chp 33)• Some applications to Biology and technology• Interference and Diffraction (Chp 35)

The Wave-Particle Debate

Newton• light consists of small

“massy” particles or corpuscles that travel in straight lines, are subject to forces as one would expect of particles but also have additional vibratory properties that can be used to explain dispersion, color produced by oil slicks and so

on.

Huyghens• light propagates as a wave

disturbance through the ether - an unseen, elastic medium pervading all of space. Light will add, cancel and share properties common to all waves.

Huyghen’s Principle

... every point on a primary wavefront serves as the source of spherical secondary wavelets propagating in the forward direction such that the primary wavefront at some later time is the envelope of these wavelets. Further, the wavelets advance with a speed and frequency equal to the primary wave at each point in space.

Mirages...

• Optical– inferior– superior (Fata Morgana)

• Acoustic

Optical Mirages

• Water on the Road?

• Fata Morgana

• Build your own mirage!

Picture Gallery

Acoustic Mirages

• The Call of the Loon?

• Voices on the Lake?

• Combine refraction, dispersion and reflection

• Illustrate subtle wave-properties of light as well

Rainbow Gallery• Spectral Order

• 1st and 2nd orders

• Alexander’s Dark Band

• Supernumeray rings

• Note the spectral order:violet inside, red outside

• Faint outer rings is the 2nd order ring or secondary bow. What do you notice about the spectral order?

• Look at the sky brightness between the primary and secondary bow.

• Beneath the primary bow there are subtle repetitions of green and violet. These “extra” arcs are called supernumary arcs.