Astronomy_Test1_Notes.docx

278 views23 pages
1 Apr 2012
Department
Course
Astronomy Chapter 1 Notes
The Scientific Method
- The Scientific Method: a way of trying to make sense of the universe
1) Observation: observe and try to understand
2) Hypothesis: make an educated guess
3) Experiment: set up an experiment
4) Conclusion: draw a conclusion on previous hypothesis
5) Next step is that someone else has to do it. it has to be reproducible from an
independent researcher
Electromagnetic Spectrum
- Astronomical information is transmitted by electromagnetic waves or starlight
- Astronomy is the only field you cannot take into the laboratory. You can only observe
and extract all possible information.
- Starlight: tells us temperature, chemical composition, motion, pressure, magnetic fields
- EM Spectrum:
- Light: mutually perpendicular oscillating electric and magnetic fields
- Light moves in a wavelike pattern at a speed of c = 3 X 10 m/s (c=speed of light)
- Theory of relativity says nothing with mass can go as fast as the speed of light
- Wavelength : distance between peaks of waves (important because it determines
colour)
- Tachyons: theoretical faster-than-light particles
- EM Spectrum: 1 X 10
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 23 pages and 3 million more documents.

Already have an account? Log in
- Default of lambda is wavelength of light
- E=mc E=energy m=mass c=speed of light
- There is a debate whether light is a little photon (a burst of energy) or a wave
- When testing whether light behaves like a wave or a particle, it behaves according to the
test you set out for it, i.e. testing if it behaves like wave it behaves like a wave and vice-
versa. Proven in the young or photoelectric test. Wave/light duality
- Photoelectric theory shows how light behaves/moves like a particle
- Magnetic and electric fields are perpendicular to one another, and velocity of light is
perpendicular to the field
- Light gives us colour
- The colour blue indicates a short wavelength while the colour red indicates a long
wavelength. In fact it is almost twice as long as blue
- To measure the wavelength of visible light the metre stick is too big. It must be measured
in nanometres which is a billionth of a metre stick
- Shorter than 400nm is ultra violet light and is extremely dangerous to your vision
- **Visible Colours: ROY G BIV (I stands for indigo)
- On test you must know the wavelength of red, violet, and green. They are 700, 400, and
550 respectively
- Photons: bundles of energy light as a particle
- With white light (mixture of all colours) each wavelength gets bent at a different angle
and white light is disbursed into different colours
- Wavelengths that are shorter than ultraviolet rays (400) are x-rays and gamma rays.
Gamma rays come from nuclear reactions
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 23 pages and 3 million more documents.

Already have an account? Log in
Shortest wavelengths to longest:
1) Gamma Rays
2) X-rays
3) Ultraviolet
4) Visible colours ROY G BIV
Wavelengths longer than red
5) Infrared (cannot see but you can detect from heat)
6) Radio Wavelengths
- Frequency = f = number of wave peaks passing a given point each second
- How many times something happens over a time unit
- Frequency is measured in waves/second = complete cycles/second = cycles/second = Hz.
Named Hertz in his honour
- **POSSIBLE TEST QUESTION: What is the frequency of green light? Speed of
light/550
- The shorter the wavelength the higher the frequency
Planck Curve
- Get star in telescope
- Put a sequence of coloured filters at the eyepiece end of a telescope
- Starlight passes through a filter and then to a computer
- Computer gives numerical value for light intensity passing through each coloured filter
- Plot of wavelengths of colour against the intensity or #of photons each second
- A Blackbody is a theoretical object that absorbs all wavelengths
- If a Blackbody is heated it will glow and emit wavelengths of whatever colour it is heated
to (a.k.a its temperature). The Planck Blackbody curve is an indication of temperature
- It will always be a curve because one of the colours will emit the most light
- Planck blackbody curve tells us the temperature of a star on the surface
- Planck curve is a graph of filter colour (=wavelength) vs. intensity (THIS WAS AKSED
ON PAST TEST BEFORE)
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 23 pages and 3 million more documents.

Already have an account? Log in

Get OneClass Grade+

Unlimited access to all notes and study guides.

Grade+All Inclusive
$10 USD/m
You will be charged $120 USD upfront and auto renewed at the end of each cycle. You may cancel anytime under Payment Settings. For more information, see our Terms and Privacy.
Payments are encrypted using 256-bit SSL. Powered by Stripe.