ch25

Question 1

luminosity

Answer 1

the total power of radiation emitted by a star

Question 2

radiant flux intensity F (or apparent brightness) equation

Answer 2

F = L/(4πd^2)

Question 3

radiant flux intensity F

Answer 3

Radiant flux intensity is the radiant power per unit area passing normally through unit area.

Question 4

A standard candle

Answer 4

is a class of stellar object which has a known luminosity and
whose distance can be determined by calculation using its radiant flux intensity (apparent brightness) and luminosity. used to determine distances to galaxies

Question 5

Cepheid variables

Answer 5

Stars whose radius varies periodically; this causes the temperature of the star to change and so the
luminosity also varies periodically.

Question 6

Wien’s displacement law

Answer 6

λmax = b/T where b is known as Wien’s displacement constant and is equal to 2.898 × 10−3mK.

Question 7

Stefan–Boltzmann law

Answer 7

For a spherical object of radius r emitting black-body radiation at thermodynamic temperature T, its luminosity L is given by the expression L = 4πσ r2 T4. where σ is the Stefan–Boltzmann constant 5.67 × 10−8

Question 8

redshift

Answer 8

lines in the emission spectra from distant objects show an increase in wavelength
from their known values

Question 9

redshift of electromagnetic radiation

Answer 9

∆λ / λ = ∆f/f = v / c (λ − λ0) is the redshift Δλ (or the blueshift) that is observed

Question 10

Hubble’s law equation

Answer 10

v ≈ H0 ×d

Question 11

hubble’s law

Answer 11

speed is directly proportional to the distance where speed is the speed of recession of a galaxy from an observer and distance is the distance from galaxy to observer