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

Telescope was invented in 1608 Pg 590 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

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 Pg 591

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

The Electromagnetic Spectrum 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

Spectrum: range of different colors with different wavelengths 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 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

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

Refracting Telescopes 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

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

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

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

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

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

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

Chapter 15 Section 1 Homework – 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?