chapter 26 l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Chapter 26 PowerPoint Presentation
Download Presentation
Chapter 26

Loading in 2 Seconds...

play fullscreen
1 / 34

Chapter 26 - PowerPoint PPT Presentation


  • 138 Views
  • Uploaded on

Chapter 26. Properties of Light. Electromagnetic Waves. Traveling, oscillating, electric and magnetic fields which are emitted by vibrating charges. The electric and magnetic fields carry energy.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Chapter 26' - freeman


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
chapter 26

Chapter 26

Properties of Light

electromagnetic waves
Electromagnetic Waves
  • Traveling, oscillating, electric and magnetic fields which are emitted by vibrating charges.
  • The electric and magnetic fields carry energy.
  • All electromagnetic waves travel at the speed of light in vacuum. (i.e.the wave speed = the speed of light)
michael faraday james clerk maxwell
Michael Faraday & James Clerk Maxwell
  • c 1831:Michael Faraday discovers electromagnetic Induction. Faraday also introduces the field-line concept for electricity and magnetism.
  • c 1865:James Clerk Maxwell develops mathematical relationships between electric and magnetic fields. Shows that all of electricity and magnetism are wave phenomena.
slide5
When Maxwell calculated the speed of these “Electro-magnetic” waves, he came up with thespeed of light.

The speed of light = constant in vacuum

c  3.00 x 108 m/s = 300,000,000m/s

  • electromagnetic wave in vacuum c = f
slide6
Note that everything you have learned about mechanical waves, with the exception of the need for a medium, also applies here to electromagnetic waves
electromagnetic spectrum
Electromagnetic Spectrum

-ray

Radio

Micro

I.R.

Visible

U.V.

X-ray

104

106

1010

1013

1023

Hz

visible part of em spectrum
Visible Part of EM Spectrum

red =700nm

fred =4.29 x 1014Hz

violet=400nm

f violet= 7.50 x 1014Hz

transparent materials
Transparent Materials
  • When light is incident on a particular material, the electrons and atoms of the material begin to vibrate while the light propagates through the material.
slide11

natural frequency of the electrons of the atoms in the material.

  • If the frequency of the light matches the:

OR

  • the vibrational frequencies of the atoms and molecules as a whole.
  • then a resonant condition is established, and the light is absorbed.
slide12
For example:

Most glass is made up of atoms (Si and other elements).

They possess electrons that have natural frequencies of vibration that closely match the frequency of ultra-violet (UV)light.

(1015- 1017) Hz

slide13

The larger atoms and molecules will vibrate at lower IR frequencies. So if IR is present, it will also be absorbed with the energy being dissipated as heat.

slide14
The visible radiation is sequentially absorbed, and then re-emitted from atom to atom. Eventually, the visible light passes through the entire piece of glass.
slide15
A state of resonance occurs for UV light.
  • We say that the glass is transparent to visible light, but not to UV or IR.
slide16

Glass

IR radiation

Visible light is transmitted

Visible light

UV radiation

UV & IR get absorbed

diffraction
Diffraction

Any bending of light by means other than reflection and refraction is called diffraction.

slide18

Light Source

Wide Window

slide19

Light Source

Interference Pattern

Narrow Slit

slide20

Two or more slits – Diffraction Grating

Light Source

Interference Pattern

Two or more slits

slide22

Polarization

The alignment of the transverse waves.

time delay between absorption and re emission of visible light
Time delay between absorption and re-emission of visible light

Medium Average speed

Vacuum c = 3 x 108 m/s

Water v = 0.75c

Glass v = 0.67c

Diamond v = 0.41c

opaque materials
Opaque Materials
  • In Opaque materials, light is absorbed without re-emission. The energy of the light including visible, goes into the internal energy of the material – heating.
slide25
Metals are opaque but reflective.
  • These free electrons are responsible for why metals make such good electrical and thermal conductors.
  • Also, the light does not propagate from atom to atom as it does in a transparent material, but goes into reflection.
shadows

Light rays from the sun are essentially parallel

Shadows

Sharp

shadow

Large far away light source

Sharp

shadow

Small nearby light source

slide27

Large nearby light source

Penumbra

(Partial shadow)

Umbra

(Total shadow)

eclipses
Eclipses

Sun

Full Moon

Not To Scale

lunar eclipse
Lunar Eclipse

Earth

Moon

Sun

Not To Scale

slide30

Solar Eclipse

Earth

Moon

Sun

SUN

Drawing Not To Scale

slide33

SOLAR

ECLIPSE