Today’s Agenda12/7/15

Check out the

Waning Crescent

Moon (17% visible)

Moonrise 3:05AM

Moonset 2:15PM & the

constellation Orion!

HomeworkNo Homework

Revisit Exploring Space

Introduction to the

Electromagnetic Spectrum

The Electromagneti

c Spectrum

And “Wavestown

”

Electromagnetic Waves

• Transverse waves without a medium! • (They can travel through empty space)

The Electromagnetic Spectrum

• The electromagnetic spectrum is just a name that scientists give a bunch of types of radiation when they want to talk about them as a group.

Long Wavelength =

Low Frequency

Short Wavelength =

High Frequency

Radio Waves

• Radio: yes, this is the same kind of energy that radio stations emit into the air for your radio to capture and turn into your favorite George Strait, Rihanna, or Faith Hill tunes.

• But radio waves are also

emitted by other things:

... such as stars and gases

in space.

• Car radios, cell phones, T-Vs,

CB radios, and walkie talkies all use

radio waves!

Microwaves

• Microwaves:

they will cook your popcorn

in just a few minutes!

o Besides microwave ovens and cell phones, other devices using the microwave range include:o GPSo WiFio Cordless home phoneso Police Traffic Radaro Military radars (e.g. ships, airplanes and satellites - these

ones can put out A LOT of power, and great caution must be taken to keep people away from the antennas because they can and will cook you like a microwave oven if you get really close, like a few feet away.)

Infrared Waves

• Infrared (IR): we often think of this as being the same thing as 'heat', because it makes our skin feel warm.

• Other ways we use infrared:• There are cameras that can pick up infrared energy,

many used in the military and in firefighting (helps locate people in smoke filled homes).

• Scopes on weapons can use infrared (night vision). • We use “heat lamps” to warm our food

(restaurants) and to keep our animals warm during cold nights.

• Telescopes used to study the stars can pick up infrared energy.

Infrared

• The image below of the center region of our galaxy was taken by IRAS (in infrared).

• The hazy, horizontal S-shaped feature that crosses the image is faint heat emitted by dust in the plane of the Solar System.

Visible Spectrum

• Visible: yes, this is the part that our eyes see.

• Visible radiation is emitted by everything from fireflies to light bulbs to stars ... also by fast-moving particles hitting other particles.

• How many objects can you think of that release light? I am sure there are hundreds!

Light Spectrum

The order in which the colors of light appear according to their frequency. They can be abbreviated as

ROY G BV which stands for:

Red, Orange, Yellow, Green, Blue, & Violet

Visible Light

• Light can be broken down into the colors of visible light with a prism.

Visible Light Spectrum

Rainbows

Ultraviolet

• Ultraviolet: we know that the Sun is a source of ultraviolet (or UV) radiation, because it is the UV rays that cause our skin to burn!

• Stars and other "hot" objects in space emit UV radiation. • People wear sunglasses to protect their eyes from the

dangerous UV radiation.• Tanning salons use this same energy in their tanning beds.• There are ultraviolet lamps that are used to kill bacteria and

sanitize areas.• We also use large telescopes to study the release of UV

radiation from objects in space.

Skin Damage from UV Radiation

Our Sun’s Harmful Ultraviolet Waves

• Our Sun emits light at all the different wavelengths in electromagnetic spectrum, but it is ultraviolet waves that are responsible for causing our sunburns.

Picture showing the UV waves coming from the

sun.

Ultraviolet

• Ultraviolet (UV) light has shorter wavelengths than visible light.

• Though these waves are invisible to the human eye, some

insects, like bumblebees, can see them!

X-Rays

• X-Rays: your doctor uses them to look at your bones and your dentist to look at your teeth. Hot gases in the Universe also emit X-rays .

• We use X-rays to:– look inside our bodies, – X-ray machines at airports to look

inside luggage– X-ray detectors to find x-ray

energy around our atmosphere in in space

– X-ray telescopes to study the

universe

How we use x-rays

Gamma-Rays

• Gamma-rays: radioactive materials can emit gamma-rays.

• When massive stars supernovae, they release a tremendous amount of energy in a “gamma ray burst”

• How we use gamma radiation:• cancer treatment • measure soil density at construction sites • ensure the proper fill level for packages of food, drugs

and other products. • sterilize medical equipment in hospitals • pasteurize certain foods and spices • gauge the thickness of metal in steel mills.

Click on the pic

Gamma-rays

• But the biggest gamma-ray generator of all is the Universe! It makes gamma radiation in all kinds of ways.

The Moon in Gamma-Rays

• The gamma-ray moon just looks like a round blob - lunar features are not visible. In high-energy gamma rays, the Moon is actually brighter than the quiet Sun. This image was taken by EGRET.

The Electromagnetic Spectrum

Radio

Microwave

Infrared

Ultraviolet

X-ray

Gamma

RedOrangeYellowGreenBlueViolet

Visible

Light

The electromagnetic spectrum is just a name that scientists give a bunch of types of radiation when they want to talk about them as a group.

“Wavestown”1. Study the picture of the town.

2. Fill in the Electromagnetic spectrum below the picture with the different forms of radiation in the proper order.

3. Color in the light spectrum (ROYGBV).

4. Identify the forms of radiant energy in the picture by numbering each example.– On the following slide, the antennae on

the Taxi is an example of radio waves

being used. It is labeled with a 1 to represent radio waves.

Radio (6) Microwave (3) IR (2)

Visible Light (9)

UV (3)X-ray (6)Gamma (1)

1

1

Radio

1

Microwave

2

2

Infrared

3

1, 2, 3, 4,5, 6, 7

Visible Light

4

4

Ultraviolet

5 5

X-Ray

6

Gamma

7

4

4

4

1

4

4

4

4

1

1

Hubble Space TelescopeHubble Space Telescope

Click on the Image

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Chandra

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X-Ray Observatory

Spitzer

Click on the Image

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Infrared Observatory