24.1 The Study of Light. Electromagnetic Radiation Includes gamma rays, X-rays, UV light, visible...
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Transcript of 24.1 The Study of Light. Electromagnetic Radiation Includes gamma rays, X-rays, UV light, visible...
24.1 The Study of Light
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
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”
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
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?
24.2 Tools for Studying Space
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
https://www.youtube.com/watch?v=VzSjqNE2AHM
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
https://www.youtube.com/watch?v=ic2aPxePlEs
Properties of Optical Telescopes
Both refracting & reflecting telescopes have 3 properties that help astronomers
Light gathering power Resolving power Magnifying power
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)
Space Telescopes
Orbit above Earth’s atmosphere & produce clearer images than Earth-based telescopes
Hubble Space Telescope
1st space telescope built by NASA
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?