Aim: How can we explain polarization and dispersion?

Do Now:

Why do athletes wear polarized sunglasses?

Incoherent Light• When light waves emitted by a

source have no special phase relationship, the light beam spreads and loses intensity quickly

Coherent Light

• Monochromatic light with most waves in phase, spreads very little and is intense

• A laser!!

• Light coming from the sun or a light bulb emit light waves that are vibrating in every plane

• We call this type of light unpolarizedunpolarized

Polarized Light• A beam of light that only

vibrates in one direction

So what happens if we add a 2nd polarizing filter oriented 90° to the 1st?

Demo

What’s Happening?

• Only transverse waves (like light) can be polarized

• Can sound waves be polarized?

NO!!!

Dispersion• When polychromatic (white) light is

passed through a prism, it is separated into its component colors

What is Polychromatic Light?

• Which light bends the least?

• Which light bends the most?

redred

violetviolet

Why?Speed of light inside prism depends on

the wavelength of light

v = fλ (f is const!!)

λred = highest

vred = highest

Red has the lowest index of refraction, therefore bends the least

Violet therefore bends the most

Dispersive Mediums

• Prisms• Air (rainbows)• Glass

Thin films of:– Water– Bubbles– Oil– Gas

• People?

Prism Spectrometer

• Disperses light into component colors

• Allows you to determine the elements the stars are made out of when attached to a telescope

Gas Tubes