What is

Light?

Light is Energy you can see.

Light Phenomenon• Isaac Newton (1642-1727) believed

light consisted of particles• By 1900 most scientists believed that

light behaved as a wave.

The sun as all stars, is a source of Natural Light

The moon is not a source of light. It is merely the sun’s light reflecting off its

surface.

Light spreads out or radiates, so is called RADIANT ENERGY

Light producing Technologies are known as Artificial Light Sources

Using Chemical Energy To produce light

Using Electrical EnergyTo produce lightLASER Technology

Incandescent Light

Incandescent light uses electricity to run through a tungsten filament which causes it to glow.

Disadvantage – only 5% of the electricity is used to generate light. The rest is lost.

Fluorescent Light

• Toxic when chemicals released to air.• Works by a gas being excited by electricity,

causing it to emit UV light.• The UV light causes the phosphorus lining to

glow.

Phosphorescence

• Items coated in phosphor which absorb UV light.

• When the light source is removed, it glows in the dark.

• T-Shirts/Wall decorations that glow in the dark

Chemiluminescence

• Light caused by a chemical reaction.

• Example: glow stick, you have to snap them to cause the chemicals to mix, and they then emit light.

Bioluminescence

• Living things that emit light.

• Some will argue that it’s a chemical reaction, which it is, but the chemicals are produced by living things.

First Basic Property of Light

LIGHT IS A FORM OF ENERGY

The Electromagnetic Spectrum- Electromagnetic spectrum represents the

range of energy from low energy to high energy.

- High Frequency to Low Frequency

Beyond Light: The Electromagnetic Spectrum

None of the frequencies found on the lower frequency end of the

electromagnet spectrum are considered particularly harmful

However, ALL the higher frequencies ARE harmful to humans.

Radio Waves

- Longest Wavelength

- Low Frequency

- Harmless to Humans

Microwaves The microwave oven cooks food by

using high frequency electromagnetic waves

Found between radio waves and visible light on the electromagnetic spectrum

Infrared Radiation

Infrared radiation is heat or thermal radiation.

Any object which has a temperature radiates in the infrared.

INTRODUCING ROY G. BIV

• R – Red • O – Orange • Y – Yellow • G – Green • B – Blue • I – Indigo• V – Violet

Visible light (for humans) is a small portion of this spectrum. This is the only part of this energy range that our eyes can detect. What we see is a rainbow of colors.

RedOrangeYellowGreenBlueIndigoViolet

ROY G BIV

The Spectrum

• Pattern of light when white light is refracted.

To produce red, all light is absorbed except red, which is reflected.

Ultraviolet Radiation

Harmful to Skin: Linked to Skin Cancer

Ultraviolet Light

Used for Security in Money

X-Rays • Even shorter wavelengths and higher

frequency.

Pass through Tissue, but are absorbed by Bone

Gamma Rays

Incredible Hulk Transformed by Gamma Rays

Instead of being transformed into a Superhero, gamma

rays will cause radiation sickness in humans and will

even cause changes in DNA. This can result in birth defects in

victims’ children many years after

exposure.

Gamma Rays • These waves are generated by radioactive atoms and in

nuclear explosions. • Gamma-rays can kill living cells, a fact which medicine uses to

its advantage, using gamma-rays to kill cancerous cells.

Laser Light

• Light • Amplification through the • Stimulated • Emission of • Radiation