Radiant Energy

Electromagnetic wave, crest, trough, medium, amplitude, wavelength, frequency,

Electromagnetic Spectrum, Visible Spectrumreflection, absorption

refraction, transparent, translucent, opaquespeed of light, scattering

Waves When energy is transmitted through matter or

space, it is known as a wave. Electromagnetic waves consist of an electric

field and a magnetic field carrying energy.

Wave

The top of a wave is called the crest The bottom of the wave is called the trough.

Unit of Light Photons are the unit of light. Think of them like

atoms, only for light instead of matter. They have no mass and have no electric charge.

Medium Medium the substance energy passes through. The speed of the wave can change based on the

medium it passes through. So light travels fastest through empty space,

slightly slower through the atmosphere, and even slower through water.

Amplitude

Amplitude is the height of the wave. The y-axis of a wave shows the amplitude.

You can think of it as the strength of the wave.

Wavelength

Wavelength is the distance between two crests on a wave.

The x-axis of the graph shows time.

Frequency

Frequency is the number of waves which pass through a single point in one second.

The length of the wave determines frequency. Hertz is the unit to measure the frequency of

waves.

Electromagnetic (EM) Spectrum

We classify different electromagnetic waves by their frequency. Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, and Gamma

EM Spectrum

Visible Light The different colors of the visible spectrum of

light are determined by their frequencies. An easy way to remember is the acronym, ROY G. BIV Red, Orange, Yellow, Green, Blue, Indigo, Violet

Reflection When a wave bounces off of something, it is

called a reflection. When you see, it is because radiation in the visible

spectrum is reflecting off of an object and hitting your eye.

Absorption

Absorption is when the photons of light are taken into matter.

The colors we see are because some of the light is absorbed and some of it is reflected.

Different chemicals absorb different frequencies of light.

Transparency

Transparent means that light can pass right through an object without being effected. The air is transparent.

Translucent objects disrupt the light, but still let it pass through.

Opaque objects are objects which light cannot pass through.

Refraction Refraction is the bending of light waves. This bending of the wave is a result of the

different speed travelled by the wave through different mediums.

The Speed of Light Light travels 300,000 km/s in a vacuum. It moves slightly

slower through air or water. (186,000 miles per second) If you could move as fast as light, you could go around

the Earth 7 and a half times in one second.

The Speed of Light Light travels 671 million miles per hour

(671,000,000 mph) Sound travels 768 miles per hour This means light travels 800,000 times faster than sound. We use this to calculate distance with lightning, if you

count 5 seconds from the lightning to thunder, it is 1 mile away.

Speed of Light Cont.

Even as fast as light travels, it takes 8.3 minutes for light to reach our planet from the sun.

The sun is 150,000,000 km away from the Earth.

Light from the Sun

Radiation comes to the Earth in three different forms.

Infrared radiation- heat Visible Light- how we see Ultraviolet Light- causes skin cancer and sun tans.

Scattering (why is the sky blue and the sun yellow?)

Because different colors have different wavelengths on the EM spectrum, they behave differently.

Blue has a much shorter wavelength then the other colors, so it is often absorbed and reflected. Causing the sky to be blue.

As the sun sets, the red color is the only wavelength long enough to reach your eyes unaffected by the atmosphere.

Scattering, cont

The Lunar Eclipse (Red Moon) is also caused by this blue light scattering effect. Travelling through the Earth’s atmosphere causes the light to become red.