1. The EM Spectrum & Earth
September 30, 2009

2. Taking Care of Business (TCB)
Read textbook Unit 22
Homework #4 – Friday, October 2

3. The Electromagnetic Spectrum
Light is an electromagnetic wave that can have a wide range of wavelengths

4. Earth’s Atmosphere

5. EM Spectrum Revisited Not all light reaches Earth’s Surface
Transparent Light
Radio
Some Infrared
Visible
Some UV
Opaque Light
Most Infrared
Most UV
X-rays
Gamma Rays

6. Discussion
What if your eyes could no longer detect visible light, but could detect infrared light? How would you see the world?
Body heat wavelengths, more red (added color).
What if you could only detect X-ray light? How would you see the world?
Bones and dense objects, metal.

7. Telescope Decision #1 Which would you fund? Why?
Project Delta – A gamma ray wavelength telescope, located in Antarctica, which will be used to look for evidence to indicate the presence of a black hole.
Would not even receive the Gamma Rays! Far away.
Project Theta – A visible wavelength telescope, located on a university campus, which will be used in the search for planets outside the solar system.
Lights are all over, problem.

8. Telescope Decision #2 Which would you fund? Why?
Project Beta – An X-ray wavelength telescope, located near the North Pole, which will be used to examine the Sun.
Project Alpha – An infrared wavelength telescope, placed on a satellite in orbit around Earth, which will be used to view supernovae.
Outside the atmosphere

9. Telescope Decision #3 Which would you fund? Why?
Project Rho – A UV wavelength telescope, placed high atop Mauna Kea in Hawaii at 14,000 feet above sea level, which will be used to look at distant galaxies.
Better science and reasonable to build.
Project Sigma – A visible wavelength telescope, placed on a satellite in orbit around Earth, which will be used to observe a pair of binary stars located in the constellation of Ursa Major.

10. Telescope Decision #4 Which would you fund? Why?
Project Zeta – A radio wavelength telescope, placed on the floor of the Mojave Desert, which will be used to detect potential communications from distant civilizations outside our Solar System.
Project Epsilon – An infrared wavelength telescope, located in the high-elevation mountains of Chile, which will be used to view newly forming stars (protostars) in the Orion nebula.
Better to observe stars than civilization that has never been discovered or detected.

11. Post Tutorial Questions
Which of the following wavelengths of light emitted by the Sun is most effectively blocked by Earth’s atmosphere?
a) visible
b) radio
c) infrared
d) gamma

12. Post Tutorial Questions
Imagine that you are the head of a funding agency that can afford to build one telescope. Which of the following proposed telescopes would be best to support?
a) a radio telescope in orbit around Earth
b) an ultraviolet telescope in orbit around Earth
c) an X-ray telescope located in New Mexico

13. Post Tutorial Questions
Which of the following wavelengths can be observed easily by a telescope located on Earth’s surface?
a) gamma ray
b) X-ray
c) ultraviolet
d) radio
e) all of the above wavelengths
f) none of the above wavelengths

14. Links to In-Class Problems
Go to astro.unl.edu
Click on “Class Action” box on right.
Light and Spectra: #2, #3, Challenge #1, Challenge #5, and Discussion #3