Electromagnetic Waves

Wave Types

Electromagnetic waves are transverse waves

Can travel through empty space We use 300,000 km/s for the velocity

Spectrum

The electromagnetic spectrum, from lowest to highest frequency Radio waves Microwaves Infrared Visible light Ultra violet X-rays Gamma rays

Visible Light

Spectrum of visible light, from lowest to highest frequency (and energy) Red Orange Yellow Green Blue Indigo Violet

Transmission

Light may pass through something, like glass, without being altered This type of material is transparent

Light may pass through material, but be altered, like frosted glass This is translucent

Some materials will not allow light to pass These are opaque

Seeing colors Light from most light bulbs, and from the sun, is

known as white light – it contains all colors of the spectrum

We see this when we use a prism or view a rainbow

We see individual colors when we observe just that frequency of light We see a shirt as red because all other colors are

absorbed and only red light is reflected to our eyes

Black?

If white light is the presence of all colors of light, what is black? Black is quiet color – it is the absence of light

When we see something as black, no (or very little) light is being reflected from the object to our eyes

The night sky looks black because there are not light sources to give light – other than the stars we see

Tinted glasses?

Since we see colors by seeing only light of that frequency We know colors of clothes is due to reflection

of light Sunglasses or colored glass allow us to see

only specific color(s) as well, but only allowing those colors to pass through the glass

All white light is not equal

White light can be made by differing “amounts” of the colors of the spectrum

We notice this difference when we see cool or warm white light bulbs Cool white has more blues, warm has more reds and

yellows Sun light has more orange and green

(see page 426 for radiation curve of sun light) Having “more” simply means that certain colors

are brighter or more intense