Modern Physics

In all nuclear reactions, remember all energy/mass and momentum is conserved.

Electromagnetic waves:

They are both waves and particles

They are also called photons (and light)

• They are waves because they have diffraction, interference, and Doppler effects
• They are particles because:
  1. they have no mass and no charge
  2. they move at the speed of light
  3. The photoelectric effect � when an electromagnetic wave strikes an electron, the electron is given off and the electromagnetic wave scatters off with less energy. And since all energy and momentum is conserved, you know the photons have mass in order to push the electron.

Energy is measured in joules. So sometimes you must convert from eV.

1 eV = 1.60*10^-19 J (it�s on the reference table)

Quantum theory:                         

Energy from light is given off /absorbed in specific amounts of energy, called a quantum of energy (or a photon of energy)

Equations:

E_photon = h � = ^hc/_λ

E_photon is in joules and is the energy of the photon.

h is plank�s constant = 6.67*10^-34 J*s

� is frequency

c is the speed of light = 3.00*10⁸ m/s

λ is wavelength

m is mass

E_i is initial energy

E_f is final energy

The E_photon is directly proportional to frequency, and indirectly proportional to the wavelength.

E_photon = E_i � E_f

This equation is used to determine how much energy there is in a photon that is released when an electron changes energy levels in an atom.

E = mc²

This means that energy is directly proportional to mass. This equation calculates how much energy there is in a given mass. This is equation is primarily used for finding the binding energy/mass defect, which is mass difference between a combined larger atom and split atom with the same number of protons, neutrons and electrons. This mass difference is called the binding energy.

Model of the atom:

1. The Thomson Model � plum pudding model � evenly spread out positive charge with electrons embedded inside it. The main point is that there are electrons.
2. The Rutherford model � was discovered by bombarding gold foil with alpha particles (positive charge) and almost all the particles went strait through, proving that most of the atom was mostly empty. But the few that dispersed proved that there was a small part of the atom was positively charged. So the model was a positive nucleus with electrons revolving around it.
3. the Bohr model �

-          electron flow around nucleus

-          each orbit is a specific distance from the nucleus

-          all forms of energy is quantized

-          An electron can gain or lose energy by changing orbits/energy levels

-          Each energy level change requires a specific amount of energy called a quanta of energy

-          An electron that stays in the same level does not lose energy even though it is accelerating towards the nucleus (centripetal force).

4. Electron Cloud model � electrons are not in energy levels, but are spread out as a cloud of negative charge.  The densest spot is the most likely place to find the electron.

Energy levels of Hydrogen:

When an electron jumps energy levels, it releases a specific photon. In order to jump a level a specific amount of energy is needed. (Ex. n=2 to n=3 requires exactly 1.89 eV for hydrogen). When it makes one jump it releases a photon (ex n=6 to n=2) but if it makes two jumps, even if the same energy is used the number of jumps made is equal to the number of photons released (ex n=6 to n=4 to n=2 to n=1 releases 3 different photons).

To calculate the energy of the photon you use the eqation E_photon = E_i � E_f  (remember to convert to joules). And then once you have the E_photon, you can us the equation          E_photon = h� = ^hc/_λ

Bright line spectrum:

When an electron jumps levels it releases a specific photon. Since the E_photon is directly proportional to the frequency, the light is always different when different photons are released.  A spectroscope is an instrument that measures all frequencies of light given of by any element depending on the element. The spectroscope releases an array of lights, called the bright line spectrum. Each element gives a different bight line spectrum because they each require different energy amounts to jump energy levels.

Forces in the universe:

Standard model:

All matter is divided into hadrons leptons and photons. 

-          Photons are particles only subject to the electromagnetic force. I.e. photon, gluon, graviton and bosons.

-          Leptons are particles subject to weak, gravitational and electromagnetic forces. I.e. electrons positrons and neutrinos.

-          Hadrons are everything subject to all 4 known forces. I.e. protons and neutrons.

o   Hadrons are divided into Baryons and Mesons

o   Baryons are elementary particles made up of 3 quarks. I.e. protons and neutrons.

o   Mesons are made up of quarks and anti-quarks. This may not make sense because anti-matter annihilate matter, but it works because the two particles come together and just revolve around each other until they collide. So while they are together, but haven�t collided yet, they are mesons.

Quarks:

Quarks are the most fundamental particles known. They have a charge of either   � ¹⁄_�3e or + ²⁄₃e. A proton, which is a baryon, is made up of 3 quarks, it has a net charge of +1, so that means that (only using regular quarks, not anti-quarks) you will need 2 (+2/3) and a (-1/3) quarks to add up to a net charge of +1. Similarly an electron needs 3 (-1/3) quarks to add up to a net charge of -1.

An anti-quark is shown by a line above symbol of the quark.

Antimatter:

Antimatter is the same thing as regular matter but with the opposite charge.  For every electron that can be made with a negative charge, there can be one made with a positive charge (positron), and same is so with all particles. When anti-matter comes into contact with matter it annihilates each other and turns into energy.

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