waves, quantum theory, and photons Flashcards
What is a wave?
A vibrating disturbance through which energy is transmitted
How are waves described?
By their height (amplitude) and length (frequency)
What is wavelength? What symbol represents it?
the length of the wave from peak to peak (top to top) or trough to trough (bottom to bottom)
lambda
What is amplitude?
distance from the middle of the wave (line in the middle) to the peak (top)
What is frequency?
the number of waves that pass through a specific point
Waves can be measured in ______ (4)
meters, centimeters, nanometers, or Angstroms
What is an angstrom?
A unit of length = to 10^-10 meters
An example of the energy of electrons acting like a wave is ______
EM radiation (flame from a fire, rays from the sun, x-ray)
What are the 7 different part of the EM spectrum? (7)
Radio, Microwaves, Infrared, Visible, Ultraviolet, X-rays, Gamma rays
Roger Makes Instruments: Violins, Ukeleles, Xylophones, and Guitars
Which part of the EM spectrum can humans see? Which part has a longer wavelength and which has a shorter wavelength? What is the acronym for the parts of this part?
the visible spectrum.
red has a longer wavelength, violet has a shorter wavelength
ROYGBIV
What is the wavelength in meters of a radio wave? Give a comparison for how big they are.
more than 1 meter. the size of buildings
What is the wavelength in meters of a microwave wave? Give comparison size
1 to 10^-3 meters
grains of sugar
What is the wavelength in meters of an infrared wave? Give comparison size
10^-3 to 7*10^-7
protozoan
What is the wavelength in meters of a visible wave? Give comparison size
710^-7 to 410^-7
bacteria
What is the wavelength in meters of an ultraviolet wave? Give comparison size
3*10^-7 to 10^-8
molecules
What is the wavelength in meters of an x-ray wave? Give comparison size
3*10^-8 to 10^-12
atoms
What is the wavelength in meters of a gamma ray? Give comparison size
less than 10^-12
atomic nuclei
A radio wave is ____ and _____
long and wide
A gama ray is _____
very small
Electrons can act like ___, but they can also act like _____
waves
particles
Who discovered that electrons can act like particles?
Max Planck
What are quanta?
small amounts (packages) of EM radiation
A quantum is the _________ that can be emitted or absorbed in the form of EM energy
smallest amount of energy
What is planck’s constant? What does it do?
Planck’s constant is 6.626 * 10^-34 Joules per second
relates the energy in 1 quantum of EM to the frequency of that same EM (represents the connection between the wave nature of light and the particle nature of light)
What is the equation for the energy of a quantum? What do all of the values mean?
E=hv or E=hc/(lambda)
E=the energy
h=planck’s constant, 6.626*10^-34
v=the frequency of the light absorbed or emitted=c/(lambda)
c=speed of light
lambda=wavelength
(hence, defines a quantum of energy, or the minimum amount of energy that can be emitted, when multiplied by the frequency of the light)
What is the speed of light?
c=3*10^8 m/s
What is quantum theory?
The study of matter and energy on atomic and subatomic levels
Energy is always emitted in _____ multiples of hv
whole number (2 hv but not 1.9 hv)
What is the photoelectric effect?
When light (that has energy above the threshold frequency) is shined on a metal surface, electrons are emitted
For the photoelectric effect, what does a brighter light mean?
This means that more electrons will be emitted
What is the threshold frequency? Why does it exist?
The frequency that the energy of the light must be above for electrons to be emitted for the photoelectric effect
Exists because electrons within metal atoms are held onto very tightly (metal atoms want to hold onto electrons) so for the electrons to be pushed out, there has to be a lot of light with a high enough frequency
The beam of light that can successfully push out electrons for the photoelectric effect is a ______, which has the same formula as ______, and hence is the same as _____
a particle called a photon
quantum
as a quantum (a photom=a quantum)
What are the characteristics of photons? (4)
1) neutral, stable, have no mass
2) interact with electrons and have energy and speed-dependent on their frequency
3) can travel at the speed of light in a vacuum
4) makes up all light and EM energy
