What is Light? Fill in the blanks on the handout. Anything written like this must go on your handout

Visible light is one of the many forms of electromagnetic radiation. It is created primarily in the sun, but is also emitted by electrons in atoms. Furthermore, light is ENERGY! And this energy travels in waves! Visible light is one of the many forms of electromagnetic radiation. It is created primarily in the sun, but is also emitted by electrons in atoms. Furthermore, light is ENERGY! And this energy travels in 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 Wavelength Distance between peaks on a wave Distance between peaks on a wave Amplitude Amplitude Wave height (from the rest position to the crest) Wave height (from the rest position to the crest) The larger the amplitude, the more energy The larger the amplitude, the more energy Frequency Frequency Rate of repetition of a wave Rate of repetition of a wave The higher the frequency, the more energy The higher the frequency, the more energy Rest position

**The energy of a wave depends on its amplitude and frequency BUT, the higher the frequency, the shorter the wavelength BUT, the higher the frequency, the shorter the wavelength These waves are called electromagnetic waves and the types of electromagnetic waves make up what is called the electromagnetic spectrum! These waves are called electromagnetic waves and the types of electromagnetic waves make up what is called the electromagnetic spectrum!

The Electromagnetic Spectrum

Light passage through materials Light may be absorbed, reflected, or transmitted Light may be absorbed, reflected, or transmitted Opaque: do not transmit light, eg. rock Opaque: do not transmit light, eg. rock Transparent: transmit light, eg. glass Transparent: transmit light, eg. glass Translucent: transmit some light, eg. Frosted glass Translucent: transmit some light, eg. Frosted glass Light may also be reflected or refracted Light may also be reflected or refracted

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

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

Eclipses Solar Eclipse: Moon blocks light from the sun Solar Eclipse: Moon blocks light from the sun So if you stand anywhere here, you cannot see the sun!

Solar Eclipse

Eclipses Lunar Eclipse: Earth blocks light from the moon Lunar Eclipse: Earth blocks light from the moon The moon will appear completely black since it is getting no light!

Lunar Eclipse

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

Bioluminescence: light released from living creatures eg. Fireflies Bioluminescence: light released from living creatures eg. Fireflies

Fluorescence: ultraviolet light activating a substance called a phosphor, which releases energy as light Fluorescence: ultraviolet light activating a substance called a phosphor, which releases energy as light Coral fluorescent under UV light Polyethylene microspheres

Practical Applications Detecting counterfeit money Detecting counterfeit money Sunblock protects from UV rays Sunblock protects from UV rays Security markers/stamps Security markers/stamps