Ch 4. light Flashcards
Clicker: What did Einstein win the Nobel Prize for?
a. E=mc2
b. Proving light is a wave
c. Proving light is a particle
d. Theory of relativity
c. proving light is a particle
define wavelength
define period
what is frequency?
wavelength= distance between peaksks
period= time between peaks
Frequency=1/ period
what is the relationship between wavelength and frequency?
inversely proportional
What is the speed o light?
c=2.9979 x 10^8 m/s
what does the energy in a wave depend on? (2) How do we increase the energy through these two properties?
Energy depends on frequency and amplitude
Frequency= more oscillations. Amplitude= higher amplitude.
Define wave
a propogation of energy that experiences inference/ diffraction
( when two waves meet, amplify or cancel out)
Why do we think of light as a wave?
carries energy
undergoes interference.
what is the wavelength range of visable light?
400nm to 700nm
When light strikes a materal, what are the four things it can do?
Reflect
transmission
absobtion
scatter
Why does the sky look blue?
Bc the atmosphere scatters blue light more than red light.
Our atmosphere behaves differently for different colours/ frequencies.
What is it transparent to?
What is it opaque to?
Trans= radio waves, vis light, some UV
Opaque to gamma, xrays, UV light blocked by upper atmosphere. Also infered, and long length radio waves
Visible light with wavelengths at the long-wavelength end
(λ=700 nm) appears as which color
red
What is thermal light produced by?
charged particles accleration/ changing state.
What are the two primary ways in which changes of state occur for light particles?
Collisions and excitations
What is black body radiation?
What dies the peak frequency correspond to?
light that is just as easily absorbed as it is emitted.
Peak freq= temperature.
Why is black body radiation useful?
Can tell temp of stars, planets, asteroids, nebula.
Clicker: A hot object that is glowing orange will become redder as it cools.
a. True
b. False
true
isotopes have different
molecular weights due to neutrons
Do electron orbitals always exhist when not full?
yes.
T/F electrons can absorb partial energies to move between orbitals.
false. must be hit by exact right frequency to be properly excited.
where does absorbtion spectra come from?
Emission spectrum?
When light is absorbed by a gas cloud.
when light is reemitted.
red shift vs blue shift. moving away vs moving towards.
why?
red shift, moving away.
blue shift, moving towards us.
bc the doppler effect. think of light as a series of waves.
What is the size of the doppler shift proportional to?
how can this help us
the radial velocity.
wwe can determine radial speeds with the doppler effect and red and blue shifts.
What is the name for the lowest energy form of electromagnetic radiation? a. Micro waves b. Radio waves c. Infrared waves d. Gamma waves
radiowaves.
An astronomer measures a source of light to have a wavelength of 900 nm. What type of light is this? Select one: a. Ultraviolet b. Microwave c. Xray d. Visible e. Infrared
infrared
Why are X-rays and gamma rays considered dangerous types of light?
because they break apart molecules thanks to their very high frequences.
At which of these temperatures would a blackbody radiate light mostly in the visible spectrum?
Select one:
a. 6000 K
b. 60000 K
c. None of these; a blackbody does not radiate visible light.
d. 600 K
e. 60 K
6000K
