Chapter 27 Outline

Mr. GaydosApril 29, 2014

Chapter 27 OutlineMajor Topics

I. Introduction II. Early Concepts of Light III. The Speed of Light IV. Electromagnetic Waves V. Light and Transparent Materials VI. Opaque Materials VII. Shadows VIII. Polarization IX. Polarized Light and 3D Viewing

Chapter 27 Outline

I. Introduction: Light is a form of radiation that makes up a relatively small part of the

Electromagnetic Spectrum that many life forms on Earth can detect.

II. Early Concepts of Light, (Section 27.1) A. Ancient Scientists,

1. Light was composed of particles. 2. Travels from eyes to the objects then back.

B. Christian Huygens provides evidence light does behaves like waves. C. Einstein’s Photo-electric Theory

1. Light consists of bundles massless particles (photons)2. Light: concentrated Electromagnetic Energy

D. Dual Nature of Light: Consists of particles called photons that behave like waves in certain circumstances

E. Important Terms.1. Diffraction:2. Photo-electric effect3. Photons

Chapter 27 Outline III. The Speed of Light, (Section 27.2)

A. Light is fast but speed is finite (has a limit) B. Speed of light = 3x10^8 m/sec. or 186,000 miles/sec.

C. Important Terms. 1. Light Year:

3x10^8 m/sec x 60 sec/min x60 min/hr. x 24hr/day x 365 day/yr

9.5 x 10^15 meters/yr. or 5.8 trillion miles/yr.

Chapter 27 Outline

IV. Electromagnetic Waves, (Section 27.3)A. Light: energy emitted by accelerating electric charges.B. Light Travel: 1. travels in Electromagnetic waves. 2. travels in Straight LinesC. We can “see” light from red (lowest frequency)

to violet (the highest frequency) D. Important Terms. 1. Electromagnetic Wave 2. Electromagnetic Spectrum 3. infrared 4. Ultraviolet

Chapter 27 Outline

V. Light and Transparent Materials (Section 27.4)A. Incident light: causes atoms to vibrateB. Light Travel in Mediums 1. As each atom vibrates, energy is

transmitted to next atom 2. Takes time for to travel through medium 3. Delay results in Slower speed in mediums

than “c” (3 x 10^8 m/s)C. Transparent Materials 1. Materials that allow light to pass through

in straight lines. 2. Examples: Clear Glass, Water, Some Crystals

Chapter 27 Outline

VI. Opaque Materials (Section 27.5)A. Materials that absorb light without re-

emitting it.B. Incident light: still results in vibration of

atoms, BUT C. Vibrations result in material becoming random kinetic energy… D. Increase in Internal Energy, they get warmer

E. Examples: Wood, Stone, Rocks, People, Clothes, Metals

Glass

• Will pass visible (Red through violet) light but

• Will not pass Ultraviolet or Infrared…Why

– At these frequencies (IR & UV) the glass absorbs the energy and does not re-emit it.

– It is __________ to these frequencies – But ___________ to visible light.

Chapter 27 OutlineVII. Shadows (Section27.6)

A. Beams of Light 1. Travel in straight Lines 2. Thin Beams called Rays 3. Wide Beams contain Bundles of

RaysB. Shadow 1. Result when Rays blocked from reaching an object 2. Total Shadow: Umbra 3. Partial Shadow: PenumbraC. Examples 1. Hand between Bright Light & one’s Eyes 2. Solar Eclipse 3. Lunar Eclipse 4. Planetary Transit (Venus 2004)

Solar Eclipse

• The Moon is between Earth & the Sun creating a Shadow on the Earth

Partial Solar EclipseApril 28 – 28, 2014

Annular Ring Eclipse

Partial Solar EclipseApril 28 – 28, 2014As seen in Australia

Lunar Eclipse

• The Earth is between the Sun & the Moon

• Blood Moon: – What is this? – What causes this?

Lunar EclipseApril 15, 2014

Chapter 27 OutlineIX. Polarization

A. Light Wave/Ray: Transverse wave1. Each Transverse Wave Vibrates in one direction2. Vertical, Horizontal, something in-between

B. Transmission of Transverse Waves (TWs) 1. No Obstructions: Waves will travel in all directions.

2. Fence like Obstruction: Only waves that line up with the spaces between vertical members pass through

Polarization Terms

C. Important Terms 1. Polarization2. Polarized3. Polarization Axis a. Vertically Polarized

b. Horizontally Polarized

Polarization (continued)X. Polarized Light & 3 D glasses

A. Humans “see” in 3 dimensions. (Depth)1. Left eye sees one image at one angle.2. Right eye sees same image at a slightly

different angle. 3. Brain builds one image from two images.4. Resulting in depth.

B. 3D Glasses1. Polarization axis of each lens fixed at 90° to each other. 2.

Optical Illusions

• Inspect each image on pg. 418 in our Text Books.

• Left to Right / Top to bottom: Answer each question associated wit each image 1-7