So.... what the actual fuck was that physics exam?!




#dc#dc comics#batman#dick grayson#bruce wayne#batfam#tim drake#batfamily#dc fanart


seen from Malaysia

seen from Russia
seen from China

seen from Croatia

seen from Malaysia

seen from Canada

seen from Croatia

seen from Germany

seen from Greece
seen from Guatemala
seen from China
seen from Ukraine

seen from United States
seen from United States

seen from United States
seen from Italy
seen from United States
seen from Greece
seen from United States

seen from Italy
So.... what the actual fuck was that physics exam?!
Last exam today yesssssssss
AS Physics G482
Quick notes Malus' law See "Malus' law" (old post, which adds more context to Malus' law)
Malus' law states that: Intensity of a wave is directly proportional to the square of the amplitude of the wave.
So Malus' law tells us that I ∝ A², where I is wave intensity (power per unit area) and A is wave amplitude.
Why I ∝ A²?
It can be shown that
wave intensity ∝ energy contained in a wave so I ∝ E
and
energy contained in a wave ∝ amplitude² so E ∝ A²
This implies that
I ∝ E ∝ A²
∴ I ∝ A²
—
This means that if we increase the wave amplitude by 4 times the original wave amplitude, we get twice the wave intensity.
And if we measure 3 times the intensity, the wave has 9 times the amplitude of the original wave.
I've now reached the 'hysterical denial' stage of revision.
If I can't see any notes/past papers/ text books then my exam does not exist
AS Physics G482
Electricity I-V characteristics
Ohmic conductor
Obeys Ohm's law because I and V remain constant.
Forward-biased diode
Has a turn on voltage required to give electrons energy = hf to create a photon of light.
Thin, metal wire
Temperature increases - I will decrease due to increase in resistance.
Thermistor
Semiconductor so I = Anev Temperature increases - n increases due to v decrease - less resistance.
AS Physics G482
Quantum physics Emission spectra
Emission spectra for an atomic gas
The angle at which the first order maxima n = 1 appears depends upon the wavelength of the light - the larger the wavelength the further distance away n = 1 will be from n = 0.
d sinθ = λn
The excited atoms only emit light at very particular wavelengths. Each element has its own particular wavelength.
Why do 'excited' atoms only emit particular wavelengths of light?
The electrons in atoms can only exist in particular energy levels. For example, in hydrogen:
0 eV means the electron is free to move.
Ground state is the lowest energy level of the electron. In hydrogen, a ground state electron requires 13.6 eV of energy to completely 'ionise' the atom (ie, to free the electron).
The electron energy levels in atoms are quantised in that they only have particular values.
Because the electron jumps to a higher energy level it must have gained energy, and due to the principle of conservation of energy it must then lose it again. It does this by jumping back down to a lower energy and releasing its energy in the form of a photon.
Energy lost ΔE (E1-E2) by the electron equals the energy E = hf of the photon emitted.
ΔE = hf
If the electron moves to a third or higher energy level, all variables of energy change must be taken into account (E1-E2, E3-E2, E3-E1) and this will produce multiple wavelengths of light due to the different photon energies.
AS Physics G482
Quantum physics The photoelectric effect
Einstein's photoelectric equation Einstein further developed Planck's theory of quantum energy. He suggested that the ultraviolet quantum of energy (hf) hitting the metal plate was used to release an electron from the surface atom, and any energy remaining became kinetic energy of the electron.
Using the law of conservation of energy he introduced the equation:
hf = ϕ + (½mv2)max
photon energy = energy to release electron + kinetic energy of electron = (work function) + KEmax
Proving Einstein's equation
KEmax = hf - ϕ y = mx + c
The threshold frequency is the lowest frequency of radiation that will result in the emission of an electron from a particular metal surface. For most metals, this frequency occurs in the ultraviolet region of the EM spectrum.
Metals that hold their surface electrons less tightly (such as sodium) will have a lower threshold frequency f = ϕ / h.