Understanding Light and the Electromagnetic Spectrum: Properties, Waves, and Energy, Papers of Astronomy

Download Understanding Light and the Electromagnetic Spectrum: Properties, Waves, and Energy and more Papers Astronomy in PDF only on Docsity! 1 Light PSC 203 Overview
In this section:
What is light?
What is the EM Spectrum? In-class activity
Discuss your answers in groups of 2
Think of as many examples light sources that you can think of.
List as many as you can on your paper.
Be prepared to turn this list in. Light
What is it?
Your thoughts? What is light?
light is an electro-magnetic wave
electric and magnetic fields oscillate
carries energy as it travels What are waves?
If light is a wave we need to understand what a wave is. 2 Waves
all waves have three related properties
speed:
how fast the wave moves
wavelength:
the distance between peaks
frequency:
how often a peak passes by Speed
the “speed of light” is very fast
c = 300,000,000 m/s = 3 x 108 m/s
c = 671,000,000 mi/hr Wavelength
the distance between peaks
You can see the wavelength of an ocean wave
You can’t “see” the wavelength of light but it works the same way Frequency
how many peaks pass a fixed point during a set amount of time
most commonly measured in Hz (Hertz)
1 Hz = 1 wave peak per second Demonstration
Looking at waves on a string to see wavelength, frequency, and speed. 5 In-class
Using tutorial on the EM Spectrum ??
Which of the following travels slowest through space? a) Radio waves. b) Visible light. c) X-rays. d) Infrared photons. e) They all travel at the same speed. ??
A photon of which color of light carries the most energy?
a. Red.
b. Yellow.
c. Green.
d. Blue.
e. All photons have the same energy. Appearance
Objects “look” different depending on what type of light is used
Need special tools to see different types of light
We can get new information by looking at different types of light Object in various light Infrared
Shows heat levels
IR goes through dust and smoke 6 X-rays
Emitted only by high energy processes
Can pass through lower density materials Ultraviolet
Emitted by medium-high energy sources
Flowers show highlighted portions near the pollen when viewed in UV (bees see UV light too)
Old bruises on human skin can sometimes be seen in UV but not visible Radio
Emitted by cold hydrogen
Can pass through solid objects (like walls)