2-1: Waves and the Electromagnetic Spectrum

What causes waves?What are the basic properties of waves?What does an electromagnetic wave consist of?What are the waves of the electromagnetic spectrum?

What is a wave?

• A wave is a disturbance that transfers energy from place to place

• Energy = the ability to do work

Properties of Waves

• Waves can be very different, but all waves share 4 basic properties:1) amplitude2) wavelength3) frequency4) speed

Amplitude = Wave height, or how far a wave moves from its rest position.

Wavelength = distance between to corresponding parts of a wave.

Crest = Highest point of wave.

Trough = Lowest point of wave.

• Frequency = number of complete waves that pass a given point in a certain amount of time

• Speed = how far a wave travels in a certain amount of time

Mechanical Waves:• Transfer energy but require

a medium to travel through• Example: Ropes, waves in

water

Electromagnetic Waves:• Transfer energy but do not

require a medium• Has vibrating electric and

magnetic fields that move through space at the speed of light

• Example: light, x-rays

Electromagnetic Waves

• Believe it or not, you are being “showered” all the time, not by rain but by waves.

What Is the Electromagnetic Spectrum?

• The electromagnetic spectrum is the complete range of electromagnetic waves placed in order of increasing frequency.

Visible light

• Electromagnetic waves you can see are called visible light

• Only a small band on the broad electromagnetic spectrum

• In order from largest to shortest wavelength: ROY G BIV (What does that stand for?)

RED, ORANGE, YELLOW, GREEN, BLUE, INDIGO, VIOLET

2-2: Visible Light and Color

How does visible light interact with an object?What determines the color of an opaque object?

When Light Strikes an Object

• When light strikes an object, the light can be reflected, transmitted, or absorbed.

• Most materials can be classified as transparent, translucent, or opaque based on what happens to light that strikes it.

Transparent Materials

• See-through• Example: clear glass• Transmits most of the light that strikes it• Particles of the material absorb the light, then

send it back out

Translucent Materials:

• Can see through it , but blurry• Example: wax paper, frosted glass• Transmits some of the light• Scatters light as it passes through material

Opaque Materials:

• Not see-through• Example: construction paper, wood• Reflects or absorbs all of the light that strikes it• Can’t see through material, because light cannot

pass through it• The color of an opaque object is the color of the

light it reflects• Example: a lemon absorbs all colors of light, but

reflects yellow light