Download The electromagnetic spectrum

The electromagnetic spectrum
What is a wave?
What is a wave?
1.a disturbance on the surface of a liquid
body, as the sea or a lake, in the form of a
moving ridge or swell.
2.any surging or progressing movement or
part resembling a wave of the sea
6.an outward curve, or one of a series of
such curves, in a surface or line; undulation.
(from Dictionary.com)
Sound is a wave
Sound is a wave
Let’s sing…
Frequency (inverse of Wavelength)
(“A” 440 Hz, or 440 oscillations per second)
Amplitude
(Timbre)
Speed = Frequency x Wavelength
Making waves with rope (frequency and energy)
Speed of sound: 350 meters / second
0.2 miles / second
The speed of sound is 0.2 miles / second.
How long does it take the sound of a
lightning strike to reach you if it occurs 0.2
miles away?
A.  0.2 seconds
B.  1 second
C.  5 seconds
D.  20 seconds
The speed of sound is 0.2 miles / second.
How long does it take the sound of a
lightning strike to reach you if it occurs 1
mile away?
A.  0.2 seconds
B.  1 second
C.  5 seconds
D.  20 seconds
Light is also a wave,
an “electromagnetic” wave
Light is also a wave
Low frequency
High frequency
6.an outward curve, or one of a
series of such curves, in a surface
or line; undulation. 6.an outward
curve, or one of a series of such
curves, in a surface or line;
undulation.
High energy
Low energy
Light is also a wave
Frequency (inverse of Wavelength)
(“yellow” light from sun has frequency
500,000,000,000,000 Hz =
500,000,000,000,000 oscillations/second )
Amplitude
(Timbre)
Speed = Frequency x Wavelength
The speed of light
Speed = Frequency x Wavelength
The speed of light is always the same!
It’s often called “c”.
It’s equal to 300,000,000 meters / second.
(3 x 108 meters/second in scientific notation)
This is equivalent to 18,641 miles per second
The speed of light is 186,000 miles/second.
How long does it take the light from a
lightning strike to reach you if it is 1 mile
away?
A.  Much, much less than 1 second
B.  3 second
C.  30 seconds
D.  300 seconds
How far away is this storm?
https://www.youtube.com/watch?v=_PqOi1C6a6Y
Speed of sound: 350 meters / second
0.2 miles / second
The speed of light is 186,000 miles/second.
How long does it take the light from a
lightning strike to reach you if it is 186,000
miles away?
A.  Much, much less than 1 second
B.  1 second
C.  30 seconds
D.  300 seconds
Light is also a particle!
Light comes in packets with:
Energy = (Planck’s constant) x (frequency of light)
We will talk about this more later in the course, when we talk
about astronomical detectors.
“Wave particle duality” is NOT intuitive. It is one of the
strange consequences of what’s called “quantum mechanics”,
invented by Einstein and others.
EM Spectrum Lecture tutorial (p. 47)
Class Action: Light and Spectra:
1 Properties of Waves
2 Sizes of Wavelengths
3 EM Spectrum parameters
4 Number line: EM spectrum
“Blackbody” emission
Everything in the universe emits light, and the color of the light is related to
the temperature of the body (hot = high energy = high frequency).
Stars of the
Pleiades
(“Subaru”)
The sun
Hot iron
Embers
Humans observed
with night vision
The “Jewel Box” cluster
This image shows the famous double star Albireo, which consists of a blue star and a yellow
star. This image was taken with a standard CCD camera, which mimics what the human eye
would see. Which of the following is true?
(A)  The blue star is hotter than the yellow star
(B)  The blue star is cooler than the yellow star
(C)  The blue and yellow star are the same temperature
(D)  It is impossible to know which star is hotter with this information
Class Action:
Light and Spectra: Challenge 7: Sirius Images