Waves Flashcards
Wavelength
distance from peak to peak, measure in nanometers for light, Lamnda
Frequency
How many complete wave lengths pass a point in one second, f, each cycle = 1 Hertz (Hz)
Velocity of a Wave
v = frequency x wavelength, speed of wave, m/s
White Light
Mixture of all colors of the spectrum in equal measures
Blue light
400 nm, shortest
Red light
750 nm, longest
Wave nature of light
Light waves can interfere with each other
Particle nature of light
Photons (Particles of light)
Photons
Packets of electromagnetic energy, E=Frequency x Planck’s constant (h), energy carried by photon is proportional to its frequency (Blue carries more energy than red)
Emission Spectrum
Distinct pattern of colored lines for each element, fingerprint for element since each is unique
Bohr Atom
Electrons travel in specific cirular orbits around the nucleus, each orbit corresponds to a fixed energy level, electron can jump between orbits by absorbing or emitting energy in the form of light, F= change in energy/ h
Bohr Atom Transitions
Level 3 to Level 1 transitions are more energetic than level 3 to level 2, Collection of all possible transitions produces an emission spectrum
Electromagnetic Spectrum
Huge range of light, not all visible,
ORDER: radio wave, microwaves, infrared, visible light, UV, x-rays, Gamma Rays
Radio Waves
Longest waves, 1mm-100km, used in radio, TV, cell phone communications, can travel long distances and through obsticles
Microwaves
1mm-1m, used in food making, satellite communication and radar, get absorbed by water molecules
Infrared (IR)
700nm-1mm, feel as heat, used in remotes, thermal imaging, and night vision glasses
Visible Light
400nm - 700nm, only EM radiation our eyes can detect, colors
Ultraviolet (UV)
10nm-400nm,, more energetic and harmful in large doses, sterilizes medical equipment, glows in black light
X - Rays
0.01nm-10nm, can pass through most materials, medical imaging
Gamma Rays
<0.01nm, most energetic, used in cancer treatment and nuclear reactions
Kirchoff’s Laws
Describe how light interacts with different types of matter
Kirchoff’s 1st Law
A hot, dense gas emits a continuous spectrum when heated
Kirchoff’s 2nd Law
A hot, low density gas emits a discreet spectrum
Kirchoff’s 3rd Law
When light of a continuous spectrum passes through a cool gas, it absorbs light at the same wavelengths that it would emit, these appear as dark lines in the spectrum (Absorption Spectrum)
Absorption Spectrum
Helps us tell what a star is made of
Transmission Spectoscophy
Star’s light passes through a planet’s atmosphere before reaching earth, certain wavelengths are absorbed by the planet’s gases, gives us the chemical composition of the planet’s atmosphere
Viens Law
Hotter Objects have their peak emission at shorter wavelengths (blue) and cooler objects have their peak wavelength at longer wavelengths (red)
Peak Wavelength
Where the radiation is the most intense, gives us the color we see, depends on the objects temp.
Wien’s Law
Used to find temp. of star if you know the peak wavelength
Wavelength Peak = 2,900,000/ Temp.(in K)
Color range of stars
From hottest to coldest
Blue, Blue-White, Yellow, Orange, Red
Doppler Effect
Change in the frequency or pitch of a sound as the source moves relative to the observer
Waves get bunched
Higher frequency, pitch, in the direction the sound is moving towards
Waves get stretched
Lower pitch as the object moves away
Blue Shift
Star is moving towards earth, has condensed wavelengths causing emission spectrum to lean towards blue
Red Shift
Star is moving away from earth, has spread out wavelengths causing emission spectrum to lean towards red
Shift Equation
If change in wavelength is < 0 blue shift
If change in wavelength is > 0 red shift
Longer wave =
Higher Frequency
Which photon has more energy red or green?
Green, higher frequency
