ASTROPHYSICS

Question 1

Apparent Magnitude

Answer 1

brightness of an object as seen from earth

Question 2

Absolute magnitude

Answer 2

Brightness seen from 10pc (parsec)

Question 3

light year

Answer 3

distance traveled by light in one year

Question 4

parsec

Answer 4

distance to an object subtending 1 second of arc to earths orbit

Question 5

State meaning of T in Stefan-Boltzmann law

Answer 5

Kelvin temperature of surface

Question 6

Unit of luminosity

Answer 6

watts

Question 7

convex/ converging lens

Answer 7

focuses incident light

Question 8

concave/ diverging lens

Answer 8

spreads out light

Question 9

focal length

Answer 9

distance between centre of a lens and principle focus

the shorter the focal length the stronger the lens

Question 10

real image

Answer 10

formed when light rays cross before refraction

Question 11

virtual image

Answer 11

formed on same side as lens, light rays do not cross

Question 12

lens formula

Answer 12

1/u + 1/v = 1/f

u - distance of object to centre of lens
v - distance of image to centre of lens
f - focal length

Question 13

power of a lens

Answer 13

shorter focal length, more powerful the lens

measured in D (dioptres)
converging (positive)
diverging (negative)
P = 1/u + 1/v = 1/f

Question 14

normal adjustment

Answer 14

sum of focal lengths of objective and eyepiece lens

Question 15

Quantum efficiency equation

Answer 15

(#electrons released) divided by
(#incident photons)

Question 16

Quantum efficiency of human eye

Answer 16

1%

Question 17

CCD advantages

Answer 17

store more images
better resolution
wider range of wavelengths detected

Question 18

What is the minimum resolving angle of the human eye

Answer 18

3.2 x 10^-4 rad or 0.02 degrees

Question 19

For us to just be able to distinguish between two diffraction patterns…

Answer 19

The central maxima of one pattern has to coincide with the other patterns first minimum

Question 20

Astronomical unit

Answer 20

1 AU is the mean distance between the Earth and the Sun.

Question 21

number of brightest star in hipparcos scale

Answer 21

1

Question 22

number of dimmest star in hippacros scale

Answer 22

6

Question 23

apparent magnitude scale based on…

Answer 23

intensity

Question 24

A stars total power output known as its…

Answer 24

luminosity

Question 25

When regions of a nebula collapse and KE of gas and dust particles increase, how does this affect temperature?

Answer 25

The temperature increases because temperature is proportional to the average kinetic energy of the gas and dust particles.

Question 26

The emitted frequency

Answer 26

the frequency of the sound wave that's emitted by a source

Question 27

Observed frequency

Answer 27

the frequency of the sound wave that reaches your ear.

Question 28

if wave speed is constant, what is the relationship of λ and f

Answer 28

inversely proportional

Question 29

Red shift

Answer 29

When an object is moving away from us (λ increases)

Question 30

Blue shift

Answer 30

When an object is moving towards us (λ decreases)

Question 31

Redshift (using absorption lines)

Answer 31

z = Δλ/λ or -Δf/f

Question 32

Recessional velocity

Answer 32

how fast a star is moving away from us

Question 33

Binary star system

Answer 33

When two objects orbit each other around a common centre of mass

Question 34

Hubble’s constant

Answer 34

v/d = H (kms^-1)(Mpc^-1) = constant

Question 35

Cosmic microwave background radiation

Answer 35

CMBR is radiation left over from the Big Bang, gamma radiation have been stretched out into microwaves (as universe is expanding).

Question 36

Hydrogen and Helium during early universe

Answer 36

75% Hydrogen 25% Helium

Question 37

Element right after big bang

Answer 37

Hydrogen

Question 38

How did helium form after the big bang

Answer 38

The temperature and pressures were so high that pairs of hydrogen nuclei began to fuse into helium

Question 39

After universe expanded the temperature and pressure…

Answer 39

dropped no more fusion of hydrogen into helium

Question 40

evidence for the Big Bang

Answer 40

-Hydrogen and Helium ratio -Red shift, objects moving away from -Cosmic Microwave Background Radiation

Question 41

age of the universe equation

Answer 41

1/H