Astrophysics

Question 1

What is apparent magnitude?

Answer 1

m - brightness measured by an observer at a specific distance

Question 2

What is absolute magnitude?

Answer 2

M - it is defined as what its apparent magnitude would be if it were 10 parsecs away from earth
it is based on the power output of an object, it does not depend on distance.

Question 3

What are the units for luminosity

Answer 3

watts

Question 4

what is the formula for luminosity

Answer 4

L = 4pie x d^2 x b where d is distance from, and b is intensity

Question 5

how do we draw convex lens’s

Answer 5

arrow pointing outwards

Question 6

how do we draw concave lens’s

Answer 6

arrows pointing inwards

Question 7

what is the principle focus

Answer 7

where the light rays meet and cross

Question 8

what is the principle axis

Answer 8

horizontal to the lens

Question 9

what is the focus length

Answer 9

distance from lens to focal point (f)

Question 10

what is magnification

Answer 10

(M) a ratio of size to actual size

Question 11

a shorter wavelength of light has a shorter focal length, which colour has the shortest focal length.

Answer 11

blue has the shortest focal length

Question 12

if the resolving power is high

Answer 12

the lower minimum angular resolution

Question 13

two light sources can only be distinguished when?

Answer 13

their airy discs from one source is at least as far as the first minimum of the other

Question 14

collecting power is proportional to what?

Answer 14

dish diameter squared or area

Question 15

how do you remember star classification

Answer 15

Oh Boy, An F Grade Kills Me.

Question 16

what is the colour of an O star

Answer 16

blue

Question 17

what is the colour of an M star

Answer 17

orange/ red

Question 18

what are the temperature ranges for an O star

Answer 18

greater than 30,000 k

Question 19

what are the temperature ranges for an B star

Answer 19

10,000 to 30,000 k

Question 20

what are the temperature ranges for an A star

Answer 20

7,500 to 10,000 k

Question 21

what are the temperature ranges for an F star

Answer 21

6,000 to 7,500 k

Question 22

what are the temperature ranges for an G star

Answer 22

5,200 to 6,000 k

Question 23

what are the temperature ranges for an K star

Answer 23

3,700 to 5,200 k

Question 24

what are the temperature ranges for an M star

Answer 24

2,400 to 3,700 k

Question 25

which class of star has strong hydrogen lines?

Answer 25

A / B

Question 26

how do you plot a black body radiation curve

Answer 26

use wines law to find the max wavelength then plot a skewed bell curve

Question 27

what special lines appear in a O star?

Answer 27

ionised helium

Question 28

what special lines appear in a B star?

Answer 28

helium, some hydrogen

Question 29

what special lines appear in a A star?

Answer 29

strong hydrogen, some ionised metals

Question 30

what special lines appear in a F star?

Answer 30

hydrogen, ionised calcium and iron

Question 31

what special lines appear in a G star?

Answer 31

neutral and ionised metals, especially calcium

Question 32

what special lines appear in a K star?

Answer 32

neutral metals, sodium

Question 33

what special lines appear in a M star?

Answer 33

strong titanium oxide, very strong sodium

Question 34

what must you refer to when comparing size of stars

Answer 34

spectral class and thus temperature

Question 35

if a star has a greater power output what else must be true?

Answer 35

it must have a larger surface area

Question 36

how can we work out the temperature of a star knowing its max wavelength of a black body radiation curve

Answer 36

wiens law

Question 37

explain what is meant by a parsec

Answer 37

distance at which the radius of the earths orbit subtends at an angle of one arc second

Question 38

if a star has the same brightness/power as another star how to we tell which is larger

Answer 38

the hotter star will be larger due to stefan's law

Question 39

why do classes A and B have the most prominent hydrogen balmer lines/

Answer 39

their temperatures are between 10 and 30 000k which is hot enough to have hydrogen in n=2 state

Question 40

describe the radial velocity method

Answer 40

the star causes a periodic doppler shift of light received due to the star orbiting a common centre of mass. red shift could then increase and decrease periodically showing there is an exoplanet orbiting

Question 41

how do we use Hubbles constant to find the age of the universe?

Answer 41

divide by 3.08x10^19 for k ms-1 Mpc-1 then 1/ans