ASP Astrophysics Fundamentals

Question 1

What is Wien's displacement law?

Accepted Answer

It states that the peak wavelength of blackbody radiation is inversely proportional to temperature

Answer

Wien's displacement law states that the peak wavelength (λmax) of blackbody radiation is inversely proportional to the absolute temperature: λmax × T = 2.898 × 10⁻³ m·K, explaining why hotter objects appear bluer.

Question 2

What is the Stefan-Boltzmann law?

Accepted Answer

A law stating that a blackbody radiates power proportional to the fourth power of its temperature

Answer

The Stefan-Boltzmann law states that the total energy radiated per unit surface area of a blackbody is proportional to the fourth power of its temperature (E = σT⁴), explaining why small temperature increases cause huge luminosity increases.

Question 3

What is Kepler's third law of planetary motion?

Accepted Answer

The square of a planet's orbital period is proportional to the cube of its semi-major axis

Answer

Kepler's third law states that P² ∝ a³, where P is the orbital period and a is the semi-major axis, meaning planets farther from the Sun take disproportionately longer to complete an orbit.

Question 4

What is the Doppler effect and how is it used in astronomy?

Accepted Answer

The change in observed frequency of waves from a moving source; used to measure radial velocities of celestial objects

Answer

The Doppler effect is the change in observed frequency or wavelength of waves emitted by a moving source; in astronomy, spectral line shifts reveal radial velocities of stars, galaxies, and gas clouds.

Question 5

What is the inverse square law of light?

Accepted Answer

The apparent brightness of a source decreases with the square of the distance from the observer

Answer

The inverse square law states that the apparent brightness (flux) of a light source decreases proportional to the square of the distance (F = L/4πd²), because light spreads over an ever-growing spherical surface.

ASP - Astronomical Society of the Pacific Exam Practice Test

ASP - Astronomical Society of the Pacific Exam Practice Test

ASP Astrophysics Fundamentals