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EM Waves
| Term | Definition |
|---|---|
| Reflecting Telescope | light captured by a curved mirror |
| Radio Telescope | Light captured by a curved metal mirror |
| Refracting Telescope | Light captured by a curved glass lens |
| Telescopes | a telescope is a device for collecting and bringing to a detector (eye/camera) electromagnetic (EM) radiation - eg. light. EM source-Telescope-Detector-Flux data on EM source |
| James Clerk Maxwell | Proved rings of Saturn had to be made of small particles. Developed electromagnetic theory of light |
| Electromagnetic Theory of Light | An electromagnetic wave is a disturbance propagated as a variation in the local electric and magnetic fields at the speed of light |
| Wave | A travelling disturbance. Any form of change or disturbance that propagates from one region to another can be thought of as a wave. |
| Frequency (f) | Number of waves crests passing per second |
| Wavelength (lambda) | Diagram 1 |
| speed = Wavelength(lambda) x frequency(f) | |
| Speed of Light | c = 3 x 10^8 m/s |
| C = lambda x f | OOTETK (units: wavelength in meters, frequency in Hertz) |
| Starlight | How stars tell us about themselves |
| The messenger | Electromagnetic (EM) radiation |
| Collecting the Message | Telescope |
| The Doppler Effect defined | Christian Doppler noted an apparent change in the observed wavelength of a signal (sound wave) as a result of motion either towards or away from an observer. |
| The Doppler Effect applied | Applies to all wave-like phenomena. Pitch increases as vehicle approaches and decreases as it moves away- the change is an apparent change - not a change in the siren's actual tone |
| Doppler Diagram | D2 and D3 |
| Doppler Interpretation | wavelength observed < wavelength if motion of source is towards observer. While wavelength observed > wavelength if motion of source is away from observer. |
| Dopplers Formula | (lamdaobs - lambda)/Lamda = V/c. -V means motion towards and +V if motion is away. |
| Motion Towards Observer | Shorter wavelength observed (blue shifted)lambdaobs - lambda |
| Motion Away from Observer | Longer wavelength observed (red shifted) |
| Proper Motion | The measured angular shift on the sky in arcseconds per year |
| Hubbles Law | There is a systematic increase in the velocity of recession of a galaxy with increasing distance |
| Hubbles Law equation OOTETK | Vgalaxy = H x Dgalaxy (where H is hubbles constant) |
| Important point about waves | They transmit information in the form of energy |
| Energy | A measure of the ability to do work. Units are Joules(J) |
| Electromagnetic Spectrum | Longest wavelengths are radio waves and shortest wavelengths are gamma rays. |
| Radiant Energy | The amount of energy E carried by an electromagnetic wave is related to its frequency. So, the greater the frequency the greater the amount of energy carried by the wave. |
| Energy Formula OOTETK | E = h x f (where h= Planck's constant) |
| Velocity formula | Velocity = distance |
| Stellar Spectra | Stars radiate most of their EM radiation at UV, visual and IR wavelengths. Absorption lines can be used to study stellar motion |
| Luminosity(L) | Total amount of EM energy radiated to all wavelengths into space per second. Units=Joules/seconds=Watts |
| Flux(F) | Energy received per square meter per second. units=Watts/m2 |
| Flux, luminosity and distance equation OOTETK | F=L/(4pie x d^2) |
| Different Wavelength Telescopes | Radio, Microwave/infared, visible, UV/Xray |
| Radio 1 | Radar studies of planets, magnetic fields, interstellar gas, galactic structure, active galaxies |
| Microwave, Infared 2 | Star formation, interstellar dust, cool stars, galactic structure |
| Visible 3 | Planets, stars, galactic structure, galaxy distribution |
| UV, X-Ray 4 | Hot interstellar medium, active galactic nuclei |
Created by:
davidvachon1
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