Week 1 biochem - Electromagnetic radiation Flashcards
what form is energy and where is it stored
energy is in waveform
the energy is stored in electric and magnetic fields
what is wavelength and frequency measured in
wavelength is measured in meters
frequency is measured in waves/second
what is the formula for energy
E= h x v
where h is planks constant
how are wavelength, frequency and energy linked
Long wavelength =
low frequency =
low energy
short-wavelength =
high frequency =
high energy
what is the energy associated with
- energy associated with electrons
- energy associated with vibrations between atoms
- energy associated with rotations of atoms relative to other electrons
what are definite packets for energy levels called
energy levels are in definite packets called quanta
energy in electromagnetic radiation is also in definite packets called photons
what happens when EM radiations strike a molecule changes its energy level
- electrons transition to a higher energy level - the level depends on the wavelength(s) of the absorbed EM
-electron return to the ground state by emitting photos of EM radiation at lower energy, and hence longer wavelength(s)
what is the difference between absorbed wavelength and emitted wavelength called
the strokes shift
what causes the difference in energy
when heat emits
what is the definition of an electron
the flow of electric charge
what is the definition of energy current
the flow of electrons (negative) or rarely (positive) ions
what is the definition of potential difference (PD) or voltage
it is work done per unit of charge when charge is moved between 2 points in an electric field. it is measured in volts
current will flow when there is a potential difference between 2 points in an electric field
how is potential difference (PD) and power supply linked
when the power supply is disconnected, then there is no PD between the electrodes
when the power supply is connected, then PD is created between electrodes
when PD is present then charged particles will flow between electrodes
what is the dual nature of light
everything in the universe from light to electrons to atoms behaves both like a particle and wave at the same time
what was Plank’s idea and how did Einstien apply his idea to light
Plank explained objects made up of oscillators could only emit light in discrete chunk units of energy that depend on the frequency of light.
Einstein said that light, which everybody knew was a wave, is really a stream of photons, each with a discrete amount of energy. this explains the way light shining on metal surfaces knocks loose electrons
who is Ernest Rutherford and what was his idea
in 1909 in England, Ernest Marsden and Hans Geiger working for Rutherford shot alpha particles at gold atoms and were stunned to find some bounced straight backwards.
this showed that most of the mass of the atom is concentrated in a tiny nucleus.
however the problem with the Rutherford atom is it can’t work,
classical physics tells us that an electron whipping around a circle emits light and we can use this to generate radio waves and x-rays.
Rutherford atom should spray x-rays in all directions for a brief instant before the electron spirals in, to crash into the nucleus.
who is Niels Bohr and what was his idea
He is a Danish theoretical physicist
he proposed that electrons in certain special orbits don’t emit any light at all. Atoms absorb and emit light only when electrons change orbits and the frequency of light depends on the energy difference (in just the way Plank and Einstien introduced it).
Bohr’s atom fixes Rutherford’s atom and explains why atoms only emit specific colours of light.
each element has its own special orbit and thus its own unique set of frequencies. however, the problem with Bohr’s atom is there is no reason for those orbits to be special.
Who is Louis de Broglie and what was his idea
He is a French PhD student
he pointed out that if the light which everyone knew was a wave behaves as a particle, maybe the electron which everyone knew is a particle behaves like a wave. (if electrons are waves, it’s easy to explain Bohr’s rule for picking out special orbits.)
nowadays there is a clear demonstration of this:
shooting single electrons at a barrier with slits cut into it.
each electron is detected at a specific place at a specific time like a particle.
but when you repeat the experiment many times all the individual electrons trace out a pattern of stripes characteristic of wave behaviour.
what happens when to take a flashlight and shine it towards a prism and then put hydrogen in the pathway
if you take a flashlight and shine it towards a prism, the white light would split up into different colours, each colour is on a different beam.
if you put hydrogen in the pathway, the light passes through the hydrogen gas and when it splits up certain colours are missing.
some colours are missing because the hydrogen absorbs certain colours and the remaining colours shine through the pyramid.
what is a photon and what is its energy
experiments have shown light sometimes acts as particles, so instead of continuous waves, light is composed of a tone of tiny little particles called photons.
the energy you see in a photon depends on the frequency of the light thus the energy depends on the colour of the light.
every single photon has an energy equal to Plank’s constant x the photon’s frequency.
how are energy and frequency linked
when frequency decreases, the energy decreases as well.
this is because energy is equal to Plank’s constant x frequency.
what is voltage
electricity is the flow of free electrons between atoms. voltage is what pushes electrons around a circuit, without voltage, electrons would move randomly in any direction.
thus only when we apply voltage to a circuit is when all the free electrons with move in the same direction causing current.
how are voltage and current linked
the more voltage we have, the more current can flow
how are voltage and potential difference linked
voltage can be referred to as potential difference, this means how much work can be potentially done by a circuit.
example
if we have a 1.5v battery, the battery has a potential difference of 1.5v between its negative and positive terminal.
if we connect a piece of wire to both terminals of the battery, then the pressure of a battery will force the electrons to flow all in the same direction along the same path.
