2-1: Waves and the Electromagnetic Spectrum

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# 2-1: Waves and the Electromagnetic Spectrum - PowerPoint PPT Presentation

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

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### 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) amplitude

2) wavelength

3) frequency

4) speed

Crest = Highest point of wave.

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

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:

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

• Transfer energy but require a medium to travel through
• Example: Ropes, waves in water
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