Stars & Galaxies 5.2 & 5.5-5.6

Convection

Hot gas rising from deeper layers of a star

Wavelength

From one crest to another, OR one trough to another.

Crest

The top “bump” on a sound or light wave

Trough

The bottom “bump” on a sound or light wave

Energy Equation

E - hc/wavelength

Red —> Indigo

Energy increases. Red has lowest energy, indigo has highest energy

Wavelength of Red

650 nm

Wavelength of Orange

590 nm

Wavelength of Yellow

570 nm

Wavelength of Green

510 nm

Wavelength of Blue

475 nm

Wavelength of Indigo

445 nm

Energy Relationship

As energy decreases, wavelength increases (inversely proportion)

As energy decreases, frequency decreases (directly proportional)

Frequency

the number of times a wave (the trough or crest) passes by per second.

Measured in Hertz (Hz) —> 1 Hz = 1 cycle/second

Wavelength and temperature relationship

As wavelength increases, temperature increases

Equation the peak of a wavelength (wien’s law)

wavelength = 3 × 10^6/ T

EM Spectrum Rays shortest to longest wavelength

gamma, x-ray, UV, Visible, infrared, microwave, radio

Visible light from shortest to longest wavelength

indigo, blue, green, yellow, orange, red

Spectrum

Light broken up as a function of wavelength (color)

the 3 ways light can be emitted by an object

continuous spectrum

emission (line) spectrum

absorption (line) spectrum

Electromagentic Spectrum

electromagnetic radiation divided into categories

Gamma Rays

Shortest wavelength.

Carries A LOT of energy.

Absorbed by Earth’s atmosphere.

X-rays

Stopped by Earth’s atmosphere.

Can penetrate tissue, but not bones.

UV (ultraviolet)

Between x-rays and visible light.

Higher energy than violet (color) does.

Also called black light

Blocked by the ozone layer

Visible Light

400-700 nm

Infrared

Humans emit infrared.

Between visible light and microwaves.

Absorbed by water and CO2

Earth’s atmosphere blocks it as it gets closer to the ground.

Microwaves

Absorbed by water vapor

Radio Waves

Divided into subsections:

Radar waves

AM Radio waves

FM & TV waves

Radar (RADI) Waves

Used for speed checks

AM (radio) Waves

broadcasting

absorbed and reflected by the ionosphere

FM & TV (radio) Waves

NOT absorbed by Earth’s atmosphere

Ionosphere

Layer of charged particles at the top of our atmosphere

Blackbody

An object that doesn’t reflect or scatter radiation, but absorbs ALL electromagnetic energy that falls into it

Power

the energy coming off per second (in watts)

Power & temperature relationship

As power increases, temperature increases

Energy Flux

Power emitted per square meter

Stefan-Boltzmann Law Equation (energy flux)

F = sigma(T)^4

sigma = 5.67 × 10^-8

Aurora’s occur in what layer of the atmosphere?

thermosphere

Ground State

State of an electron at its lowest possible energy (a lower energy level, closest to the nucleus)

Excitation

An atom is raised to a higher energy level by absorbing energy (being in an excited state).

Caused by atoms colliding

Lyman Series

Transitions to or from the ground state

This results in the emission or absorption of UV photons

Balmer Series

Transition to or form the first excited state

This produces emissions or absorptions in Visible light

Temperature and speed relationship

As temperature increases, speed increases (as well as energy)

Ionization

When an electron is removed from an atom

Ionization Energy

The minimum amount of energy required to remove an electron from its ground state

Ion

Ionized atom

Doppler Effect

If light or sound is approaching an observer, the wavelengths will be shorter (closer together).

If light or sound is moving away from an observer, the wavelengths will be longer (more spread out)

Radial Velocity

The components of an objects velocity that is going straight towards or away from the observer

Tangential Velocity

The movement of an object tangentially to an observer

Redshift

Happens when light waves are moving AWAY.

wavelength is increasing

Blueshift

Happens when light waves are moving TOWARDS an observer.

wavelength is decreasing.

Doppler Shift Formula

Change in wavelength/wavelength = Vr (radial velocity)/c (speed of light)

Change in wavelength…

redshift gives you a positive number

blueshift gives you a negative number

speed of light constant

2.997 × 10^8

total velocity

total speed of a star

use pythagorean theorem (Vt² + Vr² = V)

Paschen

When an electron jumps from a higher energy level to n=3