2Electromagnetic Radiation Includes gamma rays, X-rays, UV light, visible light, infrared radiation, microwaves, & radio wavesElectromagnetic SpectrumClassifies radiation according to wavelength & frequencyPhotons – small packet of light energyCopy diagram on pg. 674 fig. 1
4SpectroscopyThe study of the properties of light that depend on wavelengthContinuous 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”
6The 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 objectLight source that is moving away = redderLight source that is moving toward = blueDoppler Effect is used to determine whether a star or other body in space is moving away from or toward Earth
7REVIEW REVIEW REVIEWWhat types of radiation make up the electromagnetic spectrum?Compare the 3 types of spectraHow are the elements in a star determined?How can the Doppler Effect tell detection?
9Refracting Telescopes Bend or refract lightObjective 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 haloRed light is in focus = bluish halo
11Reflecting Telescopes Chromatic aberration is avoidedUse a concave mirror that focuses light in front of a mirror rather than behindMost large optical telescopes are reflectorsLight does not pass through a mirror so the glass for a reflecting telescope does not have to be of optical quality
13Properties of Optical Telescopes Both refracting & reflecting telescopes have 3 properties that help astronomersLight gathering powerResolving powerMagnifying power
14Detecting Invisible Radiation Radio telescopes – focuses the incoming radio waves on an antenna which absorbs & transmits these waves to an amplifier just like a radio antennaPoor 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)
15Space TelescopesOrbit above Earth’s atmosphere & produce clearer images than Earth-based telescopesHubble Space Telescope1st space telescope built by NASA
16REVIEW How does a refracting telescope work? Compare and contrast a refracting telescope and a reflecting telescopeHow do radio telescopes gather data?Why do space telescopes obtain clearer images than Earth based telescopes?