The importance of the Sun
1) holds 99,8% of our Solar System’s mass => gravitational poll holds and gathers planets (and all other objects) orbiting it together;
2) emits light and heat that is the only source of light in our solar system as planets reflect the only source of the Sun;
3) changes particles: solar wind interacts with planetary magnetic fields and influence planetary atmospheres
Solar wind
A stream of charged particles continually blown outward in all directions from the Sun, carrying the Sun’s magnetic field with it (in a plasma state)
4 features of the Solar System
1) planetary objects move in an organized motion (orbit in the same direction; orbit in the same direction as they rotate);
2) 2 types of planets (terrestrial and Jovian);
3) asteroids (Asteroid belt) and comets (Kuiper belt);
4) exceptions (Venus, Uranus, Earth’s Moon)
Spectrum
The range of wavelength light
(Like a rainbow where white is a mix of all colors)
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SPECTRUM
(From longest to shortest wavelengths)
Radio w —> microwave w —> infrared l —> visible l —> ultraviolet —> x-ray —> gamma waves
Wave
Smth that can transition energy without carrying material along with it
Wave length
The distance between the adjacent peaks
In meters (nm)
Frequency
The number of times that any piece of the wave moves up and down each second
In hertz
Speed of light
c ~ 300, 000 km/s (=3*10^8 m/s)
c= wavelength * frequency ==» the longer the wavelength, the lower its frequency and E (and vice versa)
Electrical charge
A fundamental physical property that describes how strongly an object interact with electromagnetic fields
Atomic terminology
Atomic number - an amount of p
Atomic mass number - an amount of p + n
Isotopes - forms of an element with the same amount of p and different amounts of n
How light and matter interact
1) emission
2) absorption
3) transmission
4) reflection/ scattering
Emission
The process in which matter emits energy in the form of light
(E.g. light bulb)
Absorption
A process by which matter absorbs E(rad.)
(E.g. heat near a bulb)
Opaque
Transmission
A process in which light passes through matter without being absorbed
(E.g. glass, air)
Transparent
Reflection/ scattering
A process by which matter changes the direction of light ——» reflection - light bounces in the same direction
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Scattering - light bounces randomly
How it works when you enter a room
Switch on the light —> bulbs starts to emit white light (with all colours) —> some light exists the room through windows —> the rest strikes surfaces of objects in the room —> material properties of objects determine the colors that are observed or reflected
Types of Spectra
1) continuous spectrum — a spectrum of light that spans a broad range of light without interruption by emission or absorption lines;
(“Bulb”»_space;>)
2) absorption line spectrum- a spectrum of light that shows dark absorption lines over the background rainbow;
(“Bulb”»_space;> dense cloud»_space;>)
On the graph: 〰️〰️⬇️⬇️⬇️
3) emission line spectrum — a spectrum of light that shows emission lines against a black background
(through dense cloud»_space;>)
On the graph: ⬆️⬆️⬆️
How light tells us what things are made off
Energy level — refers to the specific amount of energy that an e has
Dif compounds -> dif energy levels
e can escape from an atom —> ionisation —> ion — electrically charged atom
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Each atom, ion, molecule posses a unique set of energy levels. It is what causes emission and absorption lines to appear at specific wavelengths in spectra
Laws of thermal radiation
1) hotter = brighter (hotter means each square meter emits more light at ALL wavelengths)
Emitted power= sigma (const)*t^4 (temp in K)
2) hotter = bluer (higher E photons -> higher frequency)
Lambda(max)**≈2 900 000 nm/ t (in K)
**wavelengths of the maximum intensity
Doppler effect
Spectral lines shift to shorter wavelengths when an object is moving toward us, and to longer wavelengths when an object is moving away from us. | |
Blueshift Redshift
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Determines if an object is mowing away from Earth or towards Earth by comparing wavelengths (w1) to the rest wavelengths (w0)
If w(1) > w(0) - moves away (redshift)
If w(1) < (w0) - moves towards (blueshift)
Telescope properties
1) light collecting — area determines how much total light a telescope can collect: A=d^2;
2) angular resolution (detail) — the smallest angle over which we can tell that 2 dots are separate
2 types of telescopes
1) refracting (transparent lenses to collect and focus light) (used in Lab)
2) reflecting (uses a precisely curves primary mirrors to gather light that reflects it to the secondary mirror that reflects it to the focus)
Interferometry
A telescope technique in which >2 telescopes are used in tandem to produce much better (smaller) angular resolution as it would have been done by a large(er) telescope
Atmospheric effects on the visible light
1) light pollution;
2) turbulence — bends air in the continuous shifting patterns (~> twinkling of stars);
3) air atmosphere prevents most forms of light from reaching the ground at all;
≈≈> adaptive optics eliminates much of the blurring by dancing in the opposite direction of the turbulence dance (basically mirrors)
4( the atmosphere itself glows infrared wavelengths generating the background glare for most infrared observations from the ground
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=» most telescopes are above Earth’s atmosphere in space to avoid all the listed issues and make more precise images of planetary objects
