Astrophysics

Question 1

Define angular magnification

Answer 1

the angular size of an object depends on the angle the object subtends at the eye, hence the cöose to the eye, the larger it appears M=ß/a ß is angle subtended by image, a = angle subtended by object, or M = fo/fe

Question 2

Define chromatic abberation

Answer 2

lens does not focus all wavelengths of light to the same point because lenses have different refractive indexes for different wavelengths, i.e. blue travels slower and is refracted more. Resulting images will then have coloured fringes

Question 3

Define Spherical abberation

Answer 3

if a lens has a spherical shape then rays will refract at different angles, rays from the outer edge will focus closer than those that pass through central region, leading to blurred images

Question 4

Define resolving power

Answer 4

When using a telescope, the smaller the angular position, the better the resolution - more detail can be seen

Question 5

What is the rayleigh criterion?

Answer 5

Minimum angle is when the central maximum of one diffraction pattern of one image coincides with the first minimum of the other

Question 6

what is atmospheric opacity?

Answer 6

measure of the absorption of electromagnetic radiation by the atmosphere as a function of the wavelength

Question 7

define the lightyear

Answer 7

the distance travelled in one year by an electromagnetic wave in a vacuum

Question 8

define the parsec

Answer 8

the distance at which 1AU shbtends an angle of 1 arc second

Question 9

apparent magnitude

Answer 9

the relative brightness of an object as seen from earth

Question 10

absolute magnitude

Answer 10

the apparent magnitude and object would have if it were 10 prsecs away from an observer on earth

Question 11

blackbody radiation

Answer 11

an object that can absorb and emit all wavelengths of electromagnetic radiation

Question 12

Balmer series

Answer 12

series of hydrogen absorption lines which appear in the visible part of a stars spectrum when the surface temperature is greater than 7500K

Question 13

Supernova

Answer 13

an object that produces a rapid increase in its brightness

Question 14

neutron star

Answer 14

extremely debse and made of neutrons - can be a very powerful radio source due to mag fields + spinning produces pulsars

Question 15

black hole

Answer 15

object with an escape velocity greater than the speed of light