What is Light?

What are some examples of light?

Questions about Light

• Is it a wave or a particle?

• How is light produced?

• How is color determined?

• How does it travel through empty space?

• How fast does it travel?

• How does light bend, reflect, and spread out?

LIGHT

• Light travels extremely fast and over long distances

• Light carries energy and information

• Light travels in straight lines

• Light has color

• Light has different intensities/energy.

Light is both a WAVE and a PARTICLE!

Photon: a bundle of light with a certain amount of energy.

               

Light travels in waves but it is made of tiny particles called photons.

What is a wave?

A disturbance which carries energy through space

The amount of energy a light wavecarries is related to its wavelength, which is the distance between two

identical points.

Long wavelength = low energy = redShort wavelength = higher energy = violet

ROYGBIV

A sound wave is an oscillation (vibration) of air.

A water wave is an oscillation (vibration) of the surface of the water.

What is oscillating in a light wave?

The answer is electricity and magnetism!

How is Light Produced?

When an electron is energized, it moves up to a higher energy level,then falls back down releasing a

photon with a certain amount of energy!

The Electromagnetic Spectrum includes different types of waves arranged in order of their wavelength and frequency. There are 7 different types of electromagnetic waves in the spectrum.

All Electromagnetic Waves

• Carry energy in proportion to their wavelength (long wavelength = low energy)

• Are created by the motion of electric charges (electrons in atoms!!)

• Can travel through a vacuum, at the speed of c = 3.0 x 108 m/s (300,000,000 m/s)

• Are forms of “light”

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Longest wavelength:0.1 to 10,000 m-communication-telescopes-broadcasting

Wavelengths of centimetersUsed in weather forecasting (radar)

= heat radiation

Visible Light

ROYGBIV

Is really only a very small part of the entire spectrum!

Ultraviolet (UV) light has shorter wavelengths than visible light. Though these waves are invisible to the human eye, some insects, like bumblebees, can see them!

Can be seen by some insects, but not humans. Causes suntan and sunburnUsed to sterilize medical equipmentHas higher energy than visible light

Discovered by Wilhelm Roentgen, 1895

Gamma raysGamma rays have the shortest

wavelengths. They are given off by radioactive materials. They can

pass through soft materials easily, but are stopped by metals. Used for medical and agriculture reasons, as well as for safety and security!

λ less than .000000000001 meters