Electromagnetic Radiation

Radiant energy that exhibits wavelength-like behavior and travels through space at the speed of light in a vacuum.

Example: The sun light, energy used in microwave oven, the x-rays used by doctors.

Classification of Electromagnetic Radiation

The Nature of Waves

A Continuous Spectrum (a) and A Hydrogen Line Spectrum (b)

For the Hydrogen Spectrum:A Change between Two

Discrete Energy Levels—More Distance=More energy

(a)

(b)

Electrical energy is absorbed and excites the electrons to higher energy levels. The electrons then emit (give off) energy in the form of visible light.

Electricity or heat in visible light out

Energy

Ultra VioletLyman

InfraredPaschen

VisibleBalmer

65

3

2

1

4

n

Neon lights Fireworks displays Flame test and spectrum tubes

Ultraviolet (UV) energy is absorbed and excites the electrons to higher energy levels. The electrons then emit (give off) energy in the form of visible light.

UV light in visible light out

Black light posters Neon colored posters, product packages Laundry brighteners/whiteners Fluorescent dyes & inks Certain minerals/rocks

Visible and/or Ultraviolet (UV) energy is absorbed and excites the electrons to higher energy levels. The electrons then emit (give off) energy in the form of visible light with a time delay.

visible or UV light in time delay visible light out

http://web.uvic.ca/ail/techniques/Jablonski.jpg

Glow in the dark stuff Zinc sulfide—older glow-

in-the-dark material—doesn’t last as long

Strontium aluminate—newer glow-in-the-dark material—lasts much longer

http://cdn2.ioffer.com/img/item/128/809/943/gJBaVSbiNnEwYRe.jpg

Chemicals are mixed and the energy excites electrons. Instead of energy being released in the form of heat, the energy is released in the form of “cool” light. This is chemiluminesence.

If this occurs in a living organism it is called bioluminescence.

chemical energy in visible light out

http://whyfiles.org/shorties/081firefly/images/turpin_fireflies.jpg

http://courses.cm.utexas.edu/archive/Fall2001/CH210C/Syllabi/118k/118K%20Supplements_files/temp.h5.gif

Light sticks Fireflies Many deep sea

organisms

http://www.mbari.org/itd/images/retrospective/colobonema.jpg

http://static.howstuffworks.com/gif/light-stick-2.jpg

Mechanical energy excites the electrons in adhesive molecules, which then excite the electrons around nitrogen atoms in the air. The energy is then emitted in the form of visible light. (Magic tape example)

In the case of wintergreen, the methyl salicylate molecules are fluorescent, and so the mechanical energy excites the electrons in the wintergreen flavoring.

mechanical energy in visible light out

Bandage packages/Scotch® tape Crushing wintergreen candies

http://www.geocities.com/rainforest/9911/tribo.htm

The light produced is of a single phase and is combined to produce a coherent beam of light laser light.

electrical energy in coherent light emitted

Electrical energy is used to stimulate the electrons, and visible coherent light of a single phase is emitted.

Grocery store scanners Levels used in building Laser surgery

http://static.howstuffworks.com/gif/laser-level-2.jpg

http://medicineworld.org/images/blogs/12-2007/lasik-surgery-16190.jpg