Chapter 14 - The Wave Particle Duality and the Birth of Quantum Physics

As temperature increases it leads to…

increased frequency and increased brighness

what are blackbody radiation curves?

curves of brightness vs. wavelength of emission for different temperatures

what is a blackbody?

an object that completely and perfectly absorbs all light frequency that falls on it

does a blackbody reflect any of the light?

no, it absobs then re emits

what is the area under a blackbody curve?

the temperature of the blackbody

who found the explanation for blackbodies?

max planck

what was the assumption planck made?

the energy distrimbuted among the molecular oscillators is not continous but insteded consists of a finite number of very small discrete amounts, each related to the drequency of oscillation

what is a quantum?

means a fixed amount

so what did this determine about energy?

that it is a discrete quantity

what did plancks theory (which was later developed by einstein) suggest about light?

light itself was quantized

so what are the equations for energy using max plancks findings?

E = nhf or E = nhc/λ

what can the formula be used to calculate (max planck)?

the energy of one or mnore quanta of photons

when does quantization of charge become important?

when we are looking at very small objects (electrons, protons, ions, etc)

what does a photon act as?

a carrier of energy

who discovered the photoelectric effect?

Hertz

how did hertz discover the photoelectric effect

when he turned off a cathode ray, and let the high frequency light hit it causing the cathode rays to start flow

What is the photoelectric effect?

Light causes electric charges to flow

when does the photoelectric effect occur?

only above a certain thereshold called the thershold frequency

what does increasing the intensity of the external light do to the photoelectric flow?

it increases it

what does increasing the light source frequency do to the kinetic energy

it causes it to increase

what is the work function of the photoelectric effect?

energy required to overocme the binding energy with the metal surface

what happens when you increase the number of photons striking the metal surface?

you get an increase in the number of photoelectrons bumped off the surface

why does the kinetic energy of an electron increase with the frequency of light?

if the incident photon possesses more than the minimum energy any excess energy will be given to the escaping electron

Ephoton =

W + Ekelectron

what was milikans photoelectric experiment?

set up a photoelectric tube so a reversed voltage could be applied which would stop the ejected photoelectron from reaching the anode

what is the cutoff/stop voltage?

necessary voltage, prevents movement of charge

who discovered x-rays?

rontogen

how do you produce x-rays?

rapid deceleration of the electrons they strike anode

why does the rapid deceleration of electrons make x-rays

kinetic energy is converted into x-ray radiation and heat energy

can x-rays act as a wave and a particle?

yes

what are the wave characteristics of x-rays?

1. X-rays can penetrate opaque objects

   1. Will not penetrate bone

2. Can be diffracted by crystals

what are the particle characteristics of x-rays?

1. X-rays will ionize a gas

   1. Collide with electrons and drive them off the molecules to produce ions

2. X-rays will cause electron emission in water, by the same process as described above

3. X-rays will affect the photographic plates

What is the Compton Effect?

A photon of electromagnetic radiation can be regarded as a particle with a definite momentum and energy

What was the Compton Experiment?

x-rays were used to bombard electrons and measured the wavelength of the incidental and scattered x-ray through an angle theta
showed it is a purely elastic collision

meaning x-rays have a definite momentum and energy

what does the nature of light depend on?

its energy and the type of experiment done?

so the more energetic the photon?

the more particle-like its behaviour could be

what did de broglie test?

if electrons would behave like waves?

where are the debroglie equations?

top right of formula sheet (not bottom middle thats planck)

what does it mean if the waves of an electron fit in its circumference?

it has constructive interference, so it has discrete packs of interference

meaning that only waves with _______ are stable?

constructive interference

why is there no centripetal acceleration in electron orbitals?

because they act as waves and there is no acceleration in a standing wave

what are bright fringes? dark fringes?

nodes and antinodes

what do bright fringes/dark fringes have do do with probability?

bright - high probability of hitting there

dark - low probability of hitting there

what is quantum indeterminacy?

probability of a particles location