Solar Systems Exam Review 2

electromagnetic radiation / light

transport of energy, the amount of energy (E) is related to the wavelength or frequency

• E = h ∗ f = h∗(c / λ)

Interactions of Light and Matter

1. Emission 

2. Absorption

3. Transmission

4. Reflection or scattering

Emission

an object gives off light, a light source.

• ex: the Sun or a lamp.

Absorption

an object takes in light.

• ex: the green tree leaves absorb other colors besides green.

Transmission

light goes thro an object

• ex: I can see the tree outside because the window transmits visible light

Reflection or scattering

light bounces off an object.

• ex: there is a tree visible outside because sunlight bounces off of the tree

photons

“packets" of electromagnetic energy. Some are visible to our eyes (visible or optical light) and other are not (ultraviolet photons)

• All electromagnetic radiation is made of this

Crest

highest point in a wave

Trough

lwst pt on a wave

Amplitudes

height of wave ( middle to crest or middle to trough)

Wavelength

distance between successive crests (or successive troughs, or just one complete cycle of the wave)

• lambda: λ

Frequency

the number of crests that pass a certain point in a certain amount of time

Speed of light

the speed of the wave is the speed of light (c), no matter what type of photons

• v = λ∗f

• speed of wave/light = wavelength X frequency

The electromagnetic spectrum & order from short to long wavelengths

collection of all types of photons

1. Gamma ray: <0.01nm

2. X-ray

3. Ultraviolet (UV)

4. Visible (optical): 400-700nm

5. Infrared (IR)

6. Microwave

7. Radio: >10cm

Applying this to visible light colors, red has the longest wavelength and violet the shortest. That means that red has the lowest frequency and violet the highest.

Transparency of Earth’s atmosphere

we determine whether we can measure electromagnetic radiation by whether it passes thro Earth’s atmosphere as Earth’s is opaque at many wavelengths 

• Only the near-UV, visible, near-IR, and radio waves

Energy of electromagnetic radiation

Energy is directly proportional to frequency

• As frequency increases, energy increases.

Energy is inversely proportional to wavelength

• Wavelength is opposite: as wavelength increases, energy decreases.

Spectrum (spectra)

spreading light out diff wavelengths by prism or grating 

• rainbow produced is the spectrum of colors present in white light

Properties of thermal radiation

1. Hotter objects emit more light at all wavelengths (per unit area): higher temp curves never dip or cross below lower temp curves.

2. Hotter objects emit photons with a higher average energy.

The graph shows intensities across many wavelengths, but the peaks for higher temperature objects are at shorter wavelengths. This means that the average energy of those photons is also higher.

Wien’s Law: relationship between temperature and wavelength

peak of a thermal emission curve depends on the temp of the object

λ max = (constant)/ Temperature

• inverse relationship: peak wavelength decreases for higher temp objects & peak wavelength increases as you go to lower temp objects

Intensity

how bright is a particular wavelength

Relationship between wavelength and frequency 

Wavelength and frequency are inversely related for photons

• increase the frequency -> the speed stays the same, so the wavelength must decrease. And vice versa.

Kelvin

an absolute scale, 0 K (zero Kelvin) is absolute zero: nothing can be colder and there is a complete lack of motion on the atomic level.

Spectral line

sharp peak in intensity at a particular wavelength

• There is less or no emission between these spectral lines.

Continuous 

spectrum that is a smooth curve with no spikes or dips 

• solid or very dense object emits at all wavelengths depending on its temperature

• ex: visible light like a bulb shows all colors violet thro red

Emission

series of bright spectral lines

• produced by low-density, hot

• each element pattern is diff w/ distinct pattern of colors

Absorption

dark spectral lines among the colors of the rainbow, gaps in the continuous spectrum

• produced by low-density, cooler gas in front of a hotter continuous source 

• unique pattern

• ex: planet atmospheres, suns photospheres

Planet spectra and why they look like the Sun’s spectrum

They look like the Sun’s b/c the light from the Sun is being reflected onto the planet

Structure of atoms

• Nucleus

• Protons

• Neutrons 

• Electrons 

Model of hydrogen

has one proton and one electron

• commonly has no neutrons

Nucleus

neutrons, protons, electrons orbit around it 

Protons

positively charged

Neutrons

no charge

Electrons 

only have certain amounts of energy, they're restricted to certain energy levels

• can’t be at or move to energies between energy levels.

• negatively charged 

Energy levels in atoms

electrons in atoms only have certain amounts of energy (restricted to certain lvls)

structure of energy lvl depends on the atom as each atom has a unique set of energy lvl & series pf gaps between energy lvl r specific 

• absorption or emission of energy depends on gaps between energy lvls & responding photons 

Transitions between energy levels of electrons

Each transition between energy levels corresponds to a unique photon wavelength

• the photon must have the EXACT amount of energy for the electron to move between levels

Emission and absorption lines

to change energy lvls, electrons must lose or gain energy

• to go from high to low energy = photons r absorbed: electrons need to take in energy

• to go from low to high energy = photons r emitted: energy must go somewhere

Doppler effect 

Motion affects how sound waves behave differently as it approaches you than when it moves away

• Blueshift: source is approaching you, the wave crests appear closer together, meaning a shorter wavelength and a bluer color

• redshift: source is moving away from you, the wave crests appear farther apart, meaning a longer wavelength and redder color

Telescope

collect and focus light, usually using mirrors and/or lenses

• detect visible or non-visible light

• the bigger the telescope, the more light can be collected.

Light sorting instruments (spectrograph and filter)

sort the collected light before sending it to a detector which is either a

1. filter: to only look at certain wavelengths

2. spectrograph: to create a spectrum

Detector

record the light, usually by counting photons & work like a camera to sense radiation and record measurements

Refract

light passes thro lens, the change in material (air →glass→air) & curvature of lens bends the light

• bend light to converge at a pt

Reflect

light bounces off of curved mirror

• reflects light to converge 

Light collection & light gathering power

primary mirror (or lens) acts like a bucket to collect light.

• a larger "bucket" allows the telescope to collect more light and see fainter targets.

Focus point

pt where light converges is where the image appears

primary lens or mirror

largest lens or mirror which first collects the light

focal length

distance away from lens or mirror 

CCDs

made up of arrays of pixels but only count pixels & dont record wavelength/color info

• record white & black images

• count incoming photons 

  • high count → more light so brighter pixels, low counts → drker pixels 

• placed between the telescope

Resolution

high res = more details pictures 

• to get high res telescope should have lrgr pirmary mirror, interferometry (multiple telescopes wrking 2gether), & adaptive optics (make adjustments based on simultaneously measuring the atmosphere turbulence)

How a telescope forms an image

The objective (a large lens or mirror) gathers light from a distant object and forms a real, inverted image in its focal plane. The eyepiece, acting as a magnifier, then takes this intermediate image and magnifies it for your eye, producing a final, enlarged virtual image

How telescopes are funded

• publicly funded

• privately by a group or consortium