1. 24.1 The Study of Light

2. Electromagnetic Radiation
Includes gamma rays, X-rays, UV light, visible light, infrared radiation, microwaves, & radio waves
Electromagnetic Spectrum
Classifies radiation according to wavelength & frequency
Photons – small packet of light energy
Copy diagram on pg. 674 fig. 1

4. Spectroscopy
The study of the properties of light that depend on wavelength
Continuous spectrum – produced by an incandescent solid, liquid, or gas under high pressure (emit when hot)
Absorption spectrum – produced when visible light is passed through a relatively cool gas under low pressure. (gas absorbs selected wavelengths of light)
Emission Spectrum – produced by a hot gas under low pressure (bright lines)
When the spectrum of a star is studied, the spectral lines act as “fingerprints”

6. The Doppler Effect Occurs for both sound and light
Change in wavelength of a wave that is emitted from a source that is moving away or toward an object
Light source that is moving away = redder
Light source that is moving toward = blue
Doppler Effect is used to determine whether a star or other body in space is moving away from or toward Earth

7. REVIEW REVIEW REVIEW
What types of radiation make up the electromagnetic spectrum?
Compare the 3 types of spectra
How are the elements in a star determined?
How can the Doppler Effect tell detection?

8. 24.2 Tools for Studying Space

9. Refracting Telescopes
Bend or refract light
Objective lens produces an image by bending light from a distant object so that the light converges at an area called the focus (central pt.)
Chromatic aberration ( color & to go astray)
Property of a lens whereby light of diff. colors is focused at diff. places (produces a halo around it)
Blue light is in focus = reddish halo
Red light is in focus = bluish halo

11. Reflecting Telescopes
Chromatic aberration is avoided
Use a concave mirror that focuses light in front of a mirror rather than behind
Most large optical telescopes are reflectors
Light does not pass through a mirror so the glass for a reflecting telescope does not have to be of optical quality

13. Properties of Optical Telescopes
Both refracting & reflecting telescopes have 3 properties that help astronomers
Light gathering power
Resolving power
Magnifying power

14. Detecting Invisible Radiation
Radio telescopes – focuses the incoming radio waves on an antenna which absorbs & transmits these waves to an amplifier just like a radio antenna
Poor resolution (-)
Less affected by turbulence than optical telescopes (+)
Radio telescopes are hindered by human made radio interference (hidden in valleys to block these types of interference)

15. Space Telescopes
Orbit above Earth’s atmosphere & produce clearer images than Earth-based telescopes
Hubble Space Telescope
1st space telescope built by NASA

16. REVIEW How does a refracting telescope work?
Compare and contrast a refracting telescope and a reflecting telescope
How do radio telescopes gather data?
Why do space telescopes obtain clearer images than Earth based telescopes?