Astrophysics Flashcards
What is the axis of symmetry called
The principal axis
What is the principal focus
A point on the axis which is the same distance from the optical centre as the focal length. This is where light rays travelling parallel to the principal axis prior to refraction converge
Define focal length
The distance between the centre of the lens and principal focus
What does U represent in lens diagrams and equations
The distance between the object and the centre of the lens
What does V represent in lens diagrams and equations
The distance between the image and the centre of the lens, V is positive for real images and negative for virtual images
The formula for angular magnification in normal adjustment
M = angle subtended by the image / angle subtended by object at unaided eye
Equation that relates M to the focal length
M = fₒ/fₑ
3 advantages of reflecting telescopes
- Very little chromatic aberration
- Simpler to increase the size of the objective since since mirrors can be supported from behind and are lighter than lenses
- Using parabolic mirrors stops spherical aberration
Define the Rayleigh Criterion
Two objects will be just resolved if the centre of the diffraction pattern of one image coincides with the first minimum of the other
What is absolute magnitude
How bright the star would appear if it were placed 10 parsecs from Earth
What is the doppler effect
The change in wavelength and frequency of a wave as the source moves away or towards the observer
What is red shift
Shift in wavelength and frequency of waves from retreating source towards the red end of the em spectrum.
Hubbles law
The velocity of receding galaxies is proportional to their distance from Earth.
V = Hd
