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Flashcards in Light & Spectra Deck (17):

What is light?

Packet of energy described as a photon emitted by an electron dropping down an energy level.

The most important thing in astronomy!


What Young's double slit experiment?

Proves that light is both particle and wave like - when light goes through the two little gaps it creates an interference pattern.


What is Compton Scattering?

Scattering of light by electrons. The electrons can move between the layers (shell) and cause photons to be ejected when they do.


What is the Bohr Model?

Bohr Model illustrates (simply) the atom with the nucleus at the centre and electrons around the edge (in layers with the electrons strongest on the outside).


How can we use light to tell us the composition of a star or planet?

When electrons make certain jumps it emits a specific colour of photon which we can measure. Each gas emits and absorbs a very characteristic set of colours due to the different number of electrons and protons in each atom and this is how we can tell what the planets and stars are made up of.

Gas also absorbs light as well as emits light. If light is being blocked out this is also an indicator of the gas e.g. yellow blocked indicates sodium rich atmosphere.


What is a Spectroscope?

A spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials.


What is Spectroscopy?

The study of the interaction between matter and radiated energy. Everything we know is based on this technique.


What is Redshift?

Redshift determination shows up a galaxy that is moving away from us in different colours but same patterns as the universe is expanding.


What light can we see?

We see a very narrow band of light on the electromagnetic spectrum.

Between 7 x10(24) Hz (Violet i.e. hotter) and 4 x10 (24) Hz (Red i.e. cooler).


What consists of the hotter end of the electromagnetic spectrum?

Ultraviolet, X-rays and Gamma Rays i.e. shorter or high frequency wavelengths (high energy).


What consists of the cooler end of the electromagnetic spectrum?

Infrared, Microwaves and Radio waves i.e. longer or low frequency wavelengths (low energy).


How do we see gas?

Gas at different temperatures, emits light at different wavelengths. For example: using x-ray telescopes as gas emits x-rays at 0.1 to 100million degrees Celsius.


What are Radio waves?

Originate from electrons in magnetic fields.


What telescopes can see the cooler (redder) end of the spectrum?

Very Large Array (VLA), Arcminute Microkelvin Imager Large Arrange (AMILA), ALMA (under construction)

Microwave: Planck

Infrared: Akari, NASA's Spitzer, UKIRT, Herschel


What telescopes can see the hotter (bluer) end of the spectrum?

Allows hotter stars, supernova to come to the fore. Also good for finding black holes as matter gets quite hot when it falls into a black hole.

X-Ray: NASA's Chandra, XMM-Newton

Ultraviolet: SWIFT

Gamma-rays: FERMI


Name one problem with x-ray astronomy.

Interaction cross-section - x-rays are very small i.e. x-rays would actually move through the molecules of silver on a mirror. So we turn the mirror edge-on and layer the mirrors up (58 layers in XMM) so that the x-rays hit a least one molecule which allows the camera to see.


What is Hawking Radiation?

Gamma-Ray Bursts radiate from Black Holes. Very short GRB may even be Hawking Radiation.