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 High frequency Low frequency

High energy Low energy

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.

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

https://www.youtube.com/watch?v=_PqOi1C6a6Y

How far away is this storm?

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).

Hot iron The sun Embers Humans observed with night vision

Stars of the Pleiades (“Subaru”)

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