Textbook Notes (363,693)
Canada (158,533)
Physics (160)
PHYS 183 (51)
Tracy Webb (12)
Chapter 6

Chapter 6

3 Pages
Unlock Document

PHYS 183
Tracy Webb

6: Telescopes 6.2 Telescopes: Giant Eyes  2 main properties of telescopes: o light of collecting area: tells us how much total light telescope can collect at one time  characterize telescope’s size as diameter of light-collecting area (since lens is round) o angular resolution: smallest angle over which we can tell that two dots/stars are distinct  human eye has angular resolution of 1 archminute, so must have that must angular separation in sky for us to tell they are 2 stars, not 1  dependent on actually separation & distance from us  ultimate limit of telescope  properties of light o since light is an electromagnetic wave, can interfere with one another like ripples  interference limits telescope’s angular resolution  diffraction limit: angular resolution a telescope could achieve if it were limited only by interference of light waves  depends on diameter of primary mirror & wavelength of light  refracting telescope: operates like an eye, using transparent glass lenses to collect & focus light  reflecting telescope: uses precisely curved primary mirror to gather light & reflects it onto a secondary mirror which reflects the light to a focus at a place where the eye can observe it  nearly all in current research are reflecting telescopes o light passes through lens of refracting telescope so it must be made from clear, high- quality glass with precisely shaped surfaces on both sides  reflecting surface of mirror must be precisely shaped, not both sides o difficult to stabilize refracting telescopes & prevent large lenses from deforming  primary mirror of reflecting at bottom so weight less serious problem  observations through telescopes fall into 3 categories o imaging  photographs or astronomical objects  may place filters in front to allow particular colours/wavelengths  most images of astronomy are combined images of different filters  today many images made from invisible light (anything other than visible light)  no natural colour since colour is a property of visible light o spectroscopy  obtain & study spectra  spectrographs: use diffraction grating to separate various colours of light into spectra  information from image depends on angular resolution & spectral resolution  requires longer exposure time than taking an image o timing  tracks how object changes with time  results often shown as light curves  light curves: graphs that show how an object’s intensity varies with time 6.3 Telescopes and the Atmosphere  telescopes on the ground are less expensive to build, operate & maintain than telescopes in space  problems with observing from earth  daylight, weather, light pollution, blurry images by atmospheric motion, light not reaching ground  daylight  daytime sky brighter since atmosphere scatters sunlight which drowns dim light of most astronomical objects  light pollution  lights of cities scattered at night making it hard to see light of astronomical objects o placing reflective covers on tops of streetlights directs more light toward ground o low pressure lights can only be seen in a few wavelengths, so can be fi
More Less

Related notes for PHYS 183

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.