What is Light?

Write down anything that looks like this! This includes titles too!

Visible light is one of the many forms of Visible light is one of the many forms of electromagnetic radiation. It is created electromagnetic radiation. It is created primarily in the sun, but is also emitted by primarily in the sun, but is also emitted by electrons in atoms. Furthermore, light is electrons in atoms. Furthermore, light is ENERGY! And this energy travels in ENERGY! And this energy travels in waves!waves!

Properties of Waves

Rest position

Crest: highest point in a wave

Trough: lowest point in a wave

Rest position: when there are no waves

Draw this diagram!

Wavelength Distance between peaks on a wave

AmplitudeWave height (from the rest position to the

crest)The larger the amplitude, the more energy

FrequencyRate of repetition of a waveThe higher the frequency, the more energy

Rest position

**The energy of a wave depends on its **The energy of a wave depends on its amplitude and frequency amplitude and frequency BUT, the higher the frequency, the shorter the BUT, the higher the frequency, the shorter the

wavelengthwavelengthThese waves are called electromagnetic

waves and the types of electromagnetic waves make up what is called the electromagnetic spectrum!

The Electromagnetic Spectrum

Draw the wave & list the types in order

Just note that the wavelength gets smaller as you go left to right on the spectrum

Light passage through materials

Light may be absorbed, reflected, or transmittedOpaque: do not transmit light, eg. rockTransparent: transmit light, eg. glassTranslucent: transmit some light, eg.

Frosted glassLight may also be reflected or refracted

Light moves in a straight lineLight moves in a straight line

Evidence:Evidence: If you line up sheets of paper with If you line up sheets of paper with a pinhole in each of them, light will travel a pinhole in each of them, light will travel throughthrough Move the pinhole and no light will pass throughMove the pinhole and no light will pass through

ShadowsShadows

Objects block light from reaching from Objects block light from reaching from reaching an area the same shape of the reaching an area the same shape of the object, causing it to appear black object, causing it to appear black

SunSUN

Eclipses

Solar Eclipse: Moon blocks light from the sun

So if you stand anywhere here, you cannot see the sun!

Draw this!

Solar EclipseSolar Eclipse

EclipsesEclipses

Lunar Eclipse: Earth blocks light from the moon

The moon will appear completely black since it is getting no light!

Draw this!

Lunar EclipseLunar Eclipse

Luminescence

Chemiluminescence: light released during a chemical reaction, eg. Glowsticks

Bioluminescence: light released from living creatures eg. Fireflies

Fluorescence: ultraviolet light activating a substance called a phosphor, which releases energy as light

Coral fluorescent under UV light Polyethylene microspheres

Practical ApplicationsPractical Applications

Detecting counterfeit moneyDetecting counterfeit money

Sunblock protects from UV raysSunblock protects from UV rays

Security markers/stampsSecurity markers/stamps

Review Questions

Pg 469 # 4, 6, 9, 11