LIGHT (Ch. 16)

“Many hands make light work”

What makes light work?

Maxwell's Equations J.C. Maxwell 4 Equations Explain all of E-

Mag Survived since

before Einstein

What is light?

Light is... … electromagnetic waves

• Diffraction

• Interference– Double-Slit Experiment– Single-Slit Experiment

… particles• Isaac Newton called them “corpuscles”

• Photoelectric Effect

What is light?

Light is... … Umm … It cannot be both... Can it? Particles do not diffract or interfere Waves cannot cause the photoelectric effect

Whichever it is, we can use rays to describe it.

That is fast!!

The speed of light Thought to be infinite Galileo did not agree

He tried to measure the speed but was unable 17th century Dutch astronomer Ole Roemer

Calculated it to be 2.2×108 m/s Albert Michelson

Measured speed of light to be 3×108 m/s This is a constant: c = 3×108 m/s

Roy G. Biv

• Light can be separated into different types depending on (depending how you look at it) wavelength, frequency, or energy

– Radio

– Microwave

– Infrared

– Visible

– Ultraviolet

– X-Ray

– Gamma Ray

Roy G. Biv

• All we can see is called visible light, and it is a tiny portion of all light. It is further separated into colors, the colors of the rainbow

– Red

– Orange

– Yellow

– Green

– Blue

– Indigo

– Violet

Roy G. Biv

• Primary Colors of Light

– Red

– Green

– Blue

• Secondary Colors

– Cyan

– Magenta

– Yellow

• All colors together

– White

Polar Bears

• Each light wave is only oriented a certain way.

• Some materials block light that is not oriented a certain way.

• These are called polarizers.

• Polarizers can be quite useful, and interesting and fun!

– Polarized Sunglasses

– Newer 3-D glasses

Doppler Effect

• Just like sound waves, light waves can also be shifted in frequency/wavelength by the Doppler Effect.

• The equation is a little bit different, although similar

Equations

c

v

c

vff

f

c

smcv

obs

obs

light

1

/103 8

Assignment

• Chapter 16

– 14-17 (page 447)

– 52, 60, 63 (pp. 453-454)