Nature of Light, Atoms, Spectra, Doppler Effect

Sighhh... 5.0-5.6

What do spectral lines do?

They help decode what elements are in stars/galaxies

Doppler effect

Motion impacts how light waves look. They can either be spread out/bunched up depending on whether the light source is away/toward us

What type of relationship do wavelength and frequency have?

They have an inverse relationship.

Radial velocity

Movement toward/away from an observer.

Does a wave source moving toward you increase or decrease wavelength

Decrease

Blueshift

When a wave moves toward the blue end of this spectrum as the wavelength gets shorter

Redshift

When a wave length moves toward the red end of the light spectrum as the wavelength gets longer

Doppler equation

Δλ/λ=𝑣/𝑐

What happens to dark lines as a star approaches/recedes

They also widen/shrink

Electron

Negatively charged particle. Balanced by the same amount of positive charge

Nucleus

Positive-charged particle. Majority of mass is stored in nucleus

Hydrogen

Most common element in the sun/stars. One proton in nucleus, one electron orbiting the nucleus. Their attraction to each other produces the orbit.

Helium

Two protons in nucleus, two orbiting it, two nucleus. 2nd most common element

What determines an element?

The amount of protons in a nucleus

Isotopes

Elements that have the same protons but different neutrons

The Bohr Model

In order for atoms to move to orbits, it must shift its energy level by either emitting a proton or absorbing a proton

Ground state

Innermost orbit. When atoms have the lowest possible energy

Excitation

When an atom absorbs a proton and moves to a higher, outermost orbit. Doesn’t last for long.

Why do dark lines exist?

As light is remitted, it’s spread out in all directions, some directions not visible to the observer’s eye, causing these lines

How can absorption lines give info on temperature?

Absorption lines showcase electrons jumping to an outermost orbit. The hotter the temperature of a star, the more likely it is to jump to an outermost orbit.

Ionization

When an electron gets REALLY excited, it tends to leave the nucleus

Ion

Atom without an electron due to ionization

Ionization energy

The amount of energy needed to remove electrons from atoms in ground state

Electromagnetic Spectrum Mnemonic

Raging Martians Invaded Venus Using X-ray Guns. LOWEST TO HIGHEST FREQUENCY

• R – Radio waves More than 10⁹

• M – Microwaves 10⁶–10^{9 nm}

• I – Infrared 10³–10^{6 nm}

• V – Visible light 400–700 nm

• U – Ultraviolet 20–400 nm

• X – X-rays 0.01–20 nm

• G – Gamma rays less than 0.01 nm

What type of relationship do frequency and energy have?

Proportional relationship

Inverse square law

As light leaves its source, the light gets weaker and weaker

What speed to waves move at?

At the speed of light

Frequency

Number of cycles/hills per second/in a wavelength

Frequency of light

c = fλ

Why can’t we see gamma rays, x-rays, and ultraviolet

They are blocked by gases in Earth’s atmosphere

Refraction

When light bends because it passes from one transparent material to another. This is used in telescope lenses/glasses

Dispersion

Its wavelength and material influence how much light bends

Continuous spectrum

The rainbow spectra

Absorption Spectrum

Dark lines projected onto the continuous spectrum. Missing colors. This happens when white light passes through cool, thing gas

Emission Spectrum

Bright lines. Happens with HOT thin gas

What is temperature’s impact on lines?

It can make them brighter or darker

What relationship do temperature and wavelength have?

Shorter wavelength=higher temperature. Inverse relationship

What are the characteristics of short wavelengths?

Hot temperature, high energy, high frequency, blue

Wien’s law

λmax=b/T. The hotter the object, the shorter the wavelength

Energy flux

Power emitted by a star

Stefann-Boltzmann law/Emitted energy flux

Hotter the star, more energy it has. I = σT4

What determines the type of electromagnetic radiation emitted by the sun?

Temperature. It gets a temper if they don’t listen to what she determines

What creates electromagnetic radiation?

The movement of molecules/atoms creates this

What is the spectrum of visible light?

400 nm (blue) to 700 nm (red)