1. Section 1 – pg 590 Telescopes
Chapter 15
Section 1 – pg 590
Telescopes

2. Telescope was invented in 1608
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Telescope was invented in 1608
Makes distant objects appear closer
With a telescope Galileo was the first to see sunspots, Saturn’s rings, and the four large moons of Jupiter
Since Galileo better telescopes have been invented

3. Electromagnetic Radiation
Electromagnetic radiation: energy that can travel through space in the form of waves
Stars produce this during nuclear fusion
You see stars when the light they produce reach your eye
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4. Pg 591
Forms of Radiation
Visible light: all the colors you see, a type of electromagnetic radiation
Many objects give off radiation that you don’t see
Heating coils give off light and infrared radiation (heat)
Radio transmitters produce radio waves that carry signals radios and tvs

5. The Electromagnetic Spectrum
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The Electromagnetic Spectrum
Wavelength: the distance between the crest of one wave and the crest of the next wave
Visible light’s wavelength is very short
Some are 1 millionths of a meter, others are several meters long

6. Spectrum: range of different colors with different wavelengths
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Spectrum: range of different colors with different wavelengths
Visible light is made of red, orange, yellow, green, blue, indigo, violet
The electromagnetic spectrum includes the entire range of radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays

7. Pg 592
Types of Telescopes
The light from stars spreads out as it moves through space, and your eyes are too small to gather much light
This is why you cant see as many stars with just your eyes
Telescopes are instruments that collect and focus light and other forms of electromagnetic radiation
Optical telescope: a telescope that uses lenses or mirrors to collect and focus visible light
Refracting telescopes and Reflecting telescopes

8. Pg 592
Modern astronomy is based on the detection of forms of electromagnetic radiation besides visible light
Non-optical telescopes collect and focus different types of electromagnetic radiation

9. Refracting Telescopes
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Refracting Telescopes
Refracting telescope uses a convex lens to
gather and focus light
Convex lens: a piece of transparent glass, curved so that the middle is thicker than the edges
Has 2 convex lens (one at each end)
Light enters through large objective lens, which focuses it a certain distance from the lens
The larger the lens, the more light
it collects
Smaller lens at lower end is
eyepiece, which magnifies the
image

10. Reflecting Telescope Pg 593
In 1668, Isaac Newton built the first reflecting telescope
Reflecting telescope uses a curved mirror to collect and focus light
Focuses a large amount of light onto a small area
The larger the mirror, the more light the telescope can collect

11. Pg 593
Radio Telescopes
Radio Telescopes: devices used to detect radio waves from objects in space
Most radio telescopes have curved, reflecting surfaces
The curved surfaces focus faint radio waves from space
The larger a radio telescope, the more radio waves it can collect

12. Other Telescopes Some telescopes detect infrared radiation Pg 593
Other detect ultraviolet radiation, X-rays, and gamma rays

13. Pg 594
Observatories
Observatory: a building that contains one or more telescopes
Some are located in space, many are on mountaintops
Earth’s atmosphere makes objects in space look blurry
One of the best observatories on Earth is on top of Mauna Kea, a dormant volcano in Hawaii
Taller than 40% of Earth’s atmosphere

14. Pg 595
Advanced Telescope
Some new telescopes are equipped with computer systems that correct images for problems such as telescope movement and changes in air temperature or mirror shape
Other advanced telescopes uses lasers to monitor conditions in the atmosphere and change the shape of the telescope’s mirror in response

15. Pg 596
Telescopes in Space
X-rays, gamma rays and most ultraviolet radiation are blocked by Earth’s atmosphere
Use telescopes in space
Hubble Telescope collects ultraviolet, infrared radiation, and visible light
Chandra X-ray Observatory produces images in the X-ray portion of the spectrum
Spitzer Space Telescope produces images in the infrared portion of the spectrum

16. Chapter 15 Section 1 Homework – pg 596

17. 1A. List the main types of electromagnetic waves, from longest wavelength to shortest.

18. 1B. Why are images from the Hubble Space Telescope clearer than images on Earth?

19. 2A. What are the two major types of optical telescopes?

20. 2B. How does a refracting telescope work?

21. 2C. Use Figure 2 to explain the major differences between reflecting and refracting telescopes

22. 3A. How does the atmosphere affect electromagnetic radiation?

23. 3B. Why are many large optical telescopes located on mountaintops?

24. 3C. Would it make sense to place an X-ray or gamma ray telescope on a mountaintop? Explain why or why not?