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