Mock AstroPhysics Prep Flashcards
Converging Lenses?
Cause rays of light to bend towards each other
Axial Rays?
Rays parallel to principle axis
Real Image?
When light rays from a point are made to pass through another point in space
Virtual Image?
Light rays from a point on an object appear to come from another point in space
Lens Equation?
1/focal length = 1/object distance to lens + 1/lens to where image is formed
Angular Magnification?
Magnification = Angle subtended by eye at image/ angle subtended by object at unaided eye
For astronomical refracting telescope:
Angular Magnification = focal length objective lens / focal length of eyepiece lens
Refracting and Reflecting Setup Telescope Difference?
Refracting use objective and eyepiece lens whereas reflecting use primary and secondary mirrors
CCD’s compared to eye?
Quantum efficiency of ccd is 80% compared to eyes 1%. ccd detects a wider spectrum of light. Spatial resolution of the eye is 100 micrometers whereas eye is 10 micrometres which means ccds are better for finer detail. Eye field of view is 500 megapixels and CCDs is around 50 megapixels. CCD’s are less convenient as extra equipment needed
Resolving Power?
Detail of telescope
Minimum angular resolution?
Smallest angular separation at which an instrument can distinguish two points and smaller this the better resolving power
Rayleigh Criterion?
Minimum Angular Resolution = wavelength / diameter of aperture
Chromatic Aberration?
Components of light diffracted by different amounts
Spherical Aberration?
Parallel rays not converging on the same point as mirror not parabolic
Radio Telescopes?
EM radiation is reflected and focused by dish and antenna used as detector at the principal focus. Resolving power is worse than eye so telescopes linked together to counter act this.
IR and UV telescopes?
Use parabolic mirror setup to focus radiation onto a detector and CCD’s are used as radiation detectors. IR need to be more precise as they have a shorter wavelength whereas UV don’t as their wavelength is longer
X-ray telescopes?
Have series of nested mirrors to reflect x-rays from the x-rays being able to reflect from grazing mirrors and this focuses them on a detector
Collecting Power?
Proportional to collecting area otherwise dish diameter squared and is the area an objective mirror or dish
Parallax equation?
Distance to star = radius of Earth’s orbit / angle of parallax in radians
Parsec?
A star is one parsec away if the angle of parallax is equal to 1 arc second otherwise 1/2600 degrees
Light Year?
The distance electromagnetic waves travel through a vacuum in one year
Measuring distances formula?
Half subtended angle in radians = radius of object / distance to object
Luminocity?
Total amount of emitted energy in form of EM radiation each second
Intensity?
Power received from it per unit area of earth and this is the effective brightness
Apparent Magnitude difference?
1 magnitude difference is 2.51 times greater
Brightness of stars difference?
Intensity of star 2 / intensity of star 1 = 2.51 ^ apparent magnitude of star 1 - apparent magnitude of star 2
Standard Candles?
Objects that you can calculate absolute magnitude directly like a type 1a supernovae
Blackbody?
A body that absorbs all EM radiation of all wavelengths and can emit all wavelengths of EM radiation
Black body curves trends?
Peak moves towards shorter wavelength as temperature increase and so to power increase
Inverse square law intensity formula?
Intensity = Power Output / 4 pi distance^2 but to use this you have to assume the star is spherical which means it gives an even amount of power in every direction
Spectral Classes?
O = 25000 - 50000
B = 11000-25000
A = 7500 - 11000
F = 6000 - 7500
G = 5000 - 6000
K = 3500 -5000
M < 3500
