Physics and Astronomy Lecture Notes Vocabulary Exam 1

A set of vocabulary flashcards covering basic physics, radiation, Kepler's and Newton's laws, astronomical measurements, and cosmological bodies based on lecture notes.

Electromagnetic radiation

A rapidly changing electric and magnetic field that propagates through space carrying momentum and energy.

Wavelength

The distance between adjacent peaks of the field.

Frequency

The rate at which the electric and magnetic fields change, describing how fast it oscillates.

Visible light

The portion of the light spectrum with wavelengths between $400$ and $700$ that human eyes can see.

Speed of light ($c$)

A constant velocity equal to $c = 3 \times 10^8\text{ m/s} = 6.7 \times 10^8\text{ m/h}$.

Photons

Light particles with energy defined by $E = h\nu$ or $E=\frac{hc}{{}\lambda}$

Plank's constant ($h$)

A fundamental constant equal to $h = 6.67 \times 10^{-34}\text{ J s}$.

Spectrum

A band of colors, as seen in a rainbow, produced by a separation of the components of light according to wavelength.

Albedo

The fraction of light that an object reflects, ranging from $0$ to $1$.

Blackbody radiation

Radiation emitted by all dense objects, where an object's peak wavelength depends on its temperature.

Wein's constant ($b$)

A constant equal to $b = 2.96 \times 10^6\text{ nm K}$ used to find peak wavelength via $\frac{\frac{}{}{}}{\frac{}{}{}}$.

Continuous spectrum

Smooth light across a broad range of wavelengths, characteristic of blackbody radiation.

Emission line spectrum

Bright lines at a specific wavelength on a dark background.

Absorption line spectrum

Dark lines at specific wavelengths on a continuous background caused by an absorbing medium.

Element

A substance defined by the number of protons in its atom's nucleus.

Isotope

Atoms containing the same number of protons but a different number of neutrons.

Ion

An atom with an unequal number of protons and electrons, resulting in a positive or negative charge.

Lagrange points

Locations in space where satellites can orbit, such as $L2$ which is shadowed by the Earth.

Kepler's first law

The law stating that the orbit of each planet about the sun is an ellipse with the sun at one focus.

Eccentricity

The amount of flattening of an ellipse, where a perfect circular orbit is $0$ and any orbital eccentricity must be less than $1$.

Semimajor axis

Half of the major axis of an ellipse ($1\text{ AU}$).

Kepler's second law

The law stating that planets sweep out equal areas in equal times, moving faster closer to the star and slower farther away.

Perihelion

The point in an orbit when the planet is closest to the star.

Aphelion

The point in an orbit when the planet is furthest from the star.

Kepler's third law

The law stating that more distant planets orbit the Sun at a slower average speed, expressed as $P^2 = a^3$.

Inertia (Newton's first law)

The principle that an object at rest remains at rest unless acted on by an unbalanced force.

Newton's second law of motion

The law governing force, stating that force equals mass times acceleration ($F = m \times a$).

Newton's third law of motion

The law of action/reaction, stating that every action has an equal and opposite reaction.

Zenith

The point in the sky directly above your head at any given time.

Cosmology

The concept and study of the cosmos.

Retrograde motion

The apparent backward movement of a planet across the sky relative to background stars.

Prograde motion

The standard forward movement of a planet across the sky.

Apparent magnitude

A star's brightness as measured from Earth.

Absolute magnitude

A star's actual intrinsic brightness.

Precession

The slow change in the direction in which Earth's rotational axis points over time.

Stellar parallax

The apparent shift in the position of a star relative to its background when viewed from different positions.

Parsec

Parallax arcsecond; the distance from the sun to an astronomical object that has a parallax angle of $1$ arcsecond.

Astronomy

The study of objects that lie beyond our planet Earth.

Hypothesis

A potential educated explanation for an observation.

Theory

A hypothesis that has been rigorously tested and consistently supported, providing a comprehensive framework for understanding.

Comet

An icy, dusty body that often orbits the sun in a very elliptical path.

Asteroid

A small, rocky body orbiting the sun between Mars and Jupiter.

Galaxy

A group of many billions of stars orbiting around a central black hole.

Star

A large ball of gas burning hydrogen into helium and other elements through nuclear fusion in its core.

Exoplanets

Planets located outside of our solar system.

Universe

The infinite collection of all known matter and space.

Equation that givs peak wavelength

λpeak = b/T