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Chapter 15
Section 1 – pg 590Telescopes
• 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
Pg 590
Electromagnetic RadiationElectromagnetic Radiation
• Electromagnetic radiation: Electromagnetic radiation: energy that can travel energy that can travel through space in the form of wavesthrough space in the form of waves– Stars produce this during nuclear fusionStars produce this during nuclear fusion– You see stars when the light they produce reach your You see stars when the light they produce reach your
eyeeye
Pg 591Pg 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
Pg 591
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
Pg 591
• 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
Pg 591
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
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
Pg 592
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
Pg 592
Reflecting Telescope• 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
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
Pg 593
Other Telescopes• Some telescopes detect infrared radiation– Other detect ultraviolet radiation, X-rays, and gamma
rays
Pg 593
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
Pg 594
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
Pg 595
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
Pg 596
Chapter 15 Section 1Homework – pg 596
1A. List the main types of electromagnetic waves, from
longest wavelength to shortest.
1B. Why are images from the Hubble Space Telescope clearer
than images on Earth?
2A. What are the two major types of optical telescopes?
2B. How does a refracting telescope work?
2C. Use Figure 2 to explain the major differences between
reflecting and refracting telescopes
3A. How does the atmosphere affect electromagnetic radiation?
3B. Why are many large optical telescopes located on
mountaintops?
3C. Would it make sense to place an X-ray or gamma ray telescope
on a mountaintop? Explain why or why not?