I’ve taken some video clips (well Miss Horn did) of us trying out the Photoelectric effect as some people might never have seen it. I’m impressed how well it works, thanks to Mr Physics- who cleaned up the zinc plate. It needs polishing every 15 mins or so as it tarnishes very quickly and then wont work. The video of charging it positively and observing no drop in the gold leaf was just too boring to post. Hope you can watch them: I’ll have to try Plan B if not.
Here is the power point and answer from the Friday review. for more details see the Particle Adventure, as we are only touching the surface of this topic.
Click on the read more to get a glossary of the terms for this unit. I will try to update it as I think of more words that I need to add, or try the quizlet for revision
the absolute refractive index (or just the refractive index), n , of a medium is the ratio of the speed of light in a vacuum to the speed of light in the material. (also the ratio of the wavelength of light in a vacuum to the wavelength of light in the medium)
angle of incidence
the angle between the incident ray and the normal.
angle of refraction
the angle between the refracted ray and the normal.
atomic mass units (u)
by definition one twelfth of the mass of a carbon-12 nucleus.
atomic number
the number of protons in an atomic nucleus. It is this number that determines the element and its properties.
binding energy
the energy needed to split a nucleus into its separate nucleons (not on the CfE Higher course)
chain reaction
when a nucleus undergoes fission it releases neutrons that can go on to cause further fission reactions by interactions with other nuclei. If there is a sufficient concentration of suitable nuclei, the process becomes self-sustaining.
coherent waves
coherent waves are waves that have the same frequency, speed and have a constant phase relationship.
collimator
part of a spectrometer that is used to produce a parallel beam of light.
constructive interference
when waves arrive at a point in phase or crest meets a crest and trough meets a trough resulting in a wave of larger amplitude than the individual waves.
critical angle
the angle above which total internal reflections occurs. Or, the maximum value of the angle between the normal and the ray in glass, θ glass, for which refraction can occur.
destructive interference
when waves arrive at a point in out of phase or crest meets a trough resulting in a wave of smaller amplitudeas the waves cancel out.
diffraction
an effect that causes waves to bend as they go past the end of an obstacle or through a small gap in a barrier.
dispersion
the process of splitting up light into its constituent colours, this can be done with a prism and white light.
electromagnetic waves
the spectrum of waves that includes radio, visible light, X-rays etc which all have no mass and travel at the speed of light in a vacuum.
excited state
any atomic energy level higher than the ground state.
ferromagnetic
materials in which the magnetic fields of the atoms line up parallel to each other in regions known as magnetic domains.
fission
the splitting of a large atomic nucleus into smaller fragments, with the resultant release of excess energy.
gold leaf electroscope
device used to measure small amounts of charge.
grating
a transparent slide of glass or plastic that has a very large number of equally spaced grooves machined on to its surface. Each groove acts as a source for coherent beams of light.
ground state
the lowest energy level of an atom where an electron has the lowest energy level.
induced fission
the deliberate splitting of a large nucleus caused by the collision of the nucleus with a neutron.
interference
a phenomenon in which two waves superpose to form a resultant wave of greater, lower, or the same amplitude.
ionisation level
the energy level at which an electron can break free from an atom.
irradiance
the power per unit area of radiation incident on a surface.
isotopes
different forms of the same element. The isotopes of an element contain the same number of protons but have different numbers of neutrons. (Many isotopes are unstable and can emit nuclear radiation)
line absorption spectrum
a spectrum that consists of narrow dark lines across an otherwise continuous spectrum.
line emission spectrum
a spectrum consisting of narrow lines of light, the position of which depend on the substances producing the light.
magnetic domains
regions in a ferromagnetic material where the atoms are aligned with their magnetic fields parallel to each other.
magnetic field
a magnetic field is a region in which a moving charge experiences a magnetic force.
magnetic poles
one way of describing the magnetic effect, especially with permanent magnets. There are two types of magnetic poles - north and south. Opposite poles attract, like poles repel.
mass defect (do not confuse with mass difference)
the difference between the mass of a nucleus and the total mass of an equal number of individual nucleons.
mass difference
the difference in mass between the reactants and products in a nuclear reaction. The resulting mass difference is converted to energy according to the equation E=mc 2 .
mass number
the total number of nucleons (protons and neutrons) in the nucleus of an atom.
monochromatic
radiation consisting of a single frequency.
monochromatic light
light of one wavelength (and therefore one colour)
normal
a line drawn at right angles to a surface or the boundary between two different media
nucleon
the general term for protons and neutrons (contained in the nucleus).
nuclide
the nuclei of one particular isotope. These nuclei all have the same atomic number and mass number.
path difference
the difference in path lengths of two sets of waves.
phase
denotes the particular point in the cycle of a waveform.
photocathode
the terminal from which electrons will be emitted due to the photoelectric effect.
photoelectric effect
the emission of electrons from a metal due to the effect of electromagnetic radiation.
photoelectrons
free electrons produced by the photoelectric effect
photoemission
the emission of electrons from a material caused by light shining on it.
photon
the particle of electromagnetic radiation.
potential difference
the potential difference between two points is a measure of the work done in moving one coulomb of charge between the two points.
principle of reversibility
the principle of reversibility states that a ray of light will follow the same path in the opposite direction when it is reversed.
prism
a prism is a transparent optical element with flat, polished surfaces that refract light. A dispersive prism can be used to break light up into its constituent spectral colours.
quanta
a "packet" certain amount, often referring to the energy of photons.
radioactive decay series
a chain of radioactive decays as a radioactive element changes to eventually become a stable, non-radioactive element.
radioisotope
short for radioactive isotope.
radionuclide
short for radioactive nuclide.
refraction
refraction occurs when a wave goes from one medium into another. When a wave is refracted, its speed and wavelength change; its frequency remains constant; its direction sometimes changes.
spectrometer
an instrument that can make precise measurements of the spectra produced by different light sources.
spontaneous fission
the random splitting of a large atomic nucleus due to the internal processes within the nucleus. (it does not require neutrons to cause the reaction and so is not of use in a nuclear reactor).
stopping potential
the minimum voltage required to reduce photoelectric current to zero.
telescope
the part of a spectrometer through which the spectrum is viewed.
threshold frequency
the minimum frequency of electromagnetic radiation that will cause photoemission for a particular substance.
total internal reflection
when a ray of light travelling in a more dense substance meets a boundary with a less dense substance at an angle greater than the critical angle, the ray is not refracted but is all reflected inside the more dense substance.
turntable
the stage or platform of a spectrometer on which the grating or prism sits. The turntable has an angular scale on it to allow measurements to be made.
work function
the minimum energy required to cause photoemission from a substance.
For years I’ve struggled with the best way to teach force on a moving particle in a field. Tom Balanowski first introduced me to the “slap” method and this year with the help of the 2016-2017 Higher Physics Group we have got it sorted!
Use the Left-hand Slap Rule where the four fingers of the left point in the direction of the magnetic field B and the thumb points in the direction of the moving charge or current, the direction of slapping would be the direction of force F on the conductor.
So how to deal with positive and negative charges. We decided that this method can be used for both. If the charge is negative the slap is the way the palm points. If the charges are positive then use the back of the hand, which is far more Painful
Pain = Positive
Thanks to Amy for these! Note the arrow for the force, should really be coming out of the hand or the way the slap goes; Amy drew this on her hand before I had told her about the × and • -kinaesthetic learner!
Powers of Ten- this was high tech when I was at school!
Since then a few things have moved on, not least with the physics as well as the graphics.
Orders of Magnitude
The class of scale or magnitude of any amount, where each class contains values of a fixed ratio (most often 10) to the class preceding it. For example, something that is 2 orders of magnitude larger is 100 times larger; something that is 3 orders of magnitude larger is 1000 times larger; and something that is 6 orders of magnitude larger is one million times larger, because 102 = 100, 103 = 1000, and 106 = one million
In its most common usage, the amount scaled is 10, and the scale is the exponent applied to this amount (therefore, to be an order of magnitude greater is to be 10 times, or 10 to the power of 1, greater).
Orders of magnitude are generally used to make very approximate comparisons and reflect very large differences. If two numbers differ by one order of magnitude, one is about ten times larger than the other. If they differ by two orders of magnitude, they differ by a factor of about 100. Two numbers of the same order of magnitude have roughly the same scale — the larger value is less than ten times the smaller value.
Source: Boundless. “Order of Magnitude Calculations.” Boundless Physics Boundless, 26 May. 2016. Retrieved 23 Jan. 2017 from https://www.boundless.com/physics/textbooks/boundless-physics-textbook/the-basics-of-physics-1/significant-figures-and-order-of-magnitude-33/order-of-magnitude-calculations-203-6080/
A proton is 3 orders of magnitude larger than a positron or electron.
Below are the updated 2019 versions. Currently the book is divided into the Standard Model, Forces and Particles and Nuclear Radiation in Part 1 and the waves part will be in part 2, which I have yet to finalise. If you want a colour copy, then you’re welcome to print it out at your own cost.on
P&W ANSWERS Now most of the notes are complete I can start working through the answers. I have got these in a jotter, but will plod through them as quick as I can. They are very slow to type up in equation editor.
…and finally the Particles and Waves book 2 is finished.
The following two documents are a wonderful summary of the Particles and Waves topic from the Revised Higher course courtesy of George Watson’s College, which is very much the current CfE Higher Course.
quantum model of atom Mrs Physics’ model of energy level, to help you remember, not necessarily to teach you Physics!
quantum model of atom answers Mrs Physics’ model of energy level answers. Don’t look at these until you’ve tried them yourself!
These are the tweets from the higher class this 2017. Describe in under 140 characters the following words. Let us know if you can do better. Some of the tweets are a little over as there are no symbols in wordpress that I can find.
TERM
DEFINITION (140 characters or less)
#4 FUNDAMENTAL FORCES
Fundamental forces: interactions that cannot be reduced. There are 4 types. The forces keep all matter together in the universe.
#ANNIHALATE
Process in which a particle and antiparticle unite, annihilate each other, and produce 1 or more photons. Energy and momentum are conserved.
#ANTIMATTER
Matter consisting of elementary particles which are the antiparticles of those making up normal matter.
#BARYON
A subatomic particle which contains 3 quarks. Baryons are hadrons.
#BOSON
A subatomic particle, such as a photon, which has zero or integral spin. All the force carrier particles are bosons.
#COLOUR
Particle has 3 apparently identical quarks but have different properties categorised by colour to satisfy Pauli Exclusion Principle
#ELECTROMAGNETIC FORCE
1 of 4 fundamental forces. influencing electrically charged particles. Responsible for electricity, magnetism and light and holds p+ and e- together
#ELECTROMAGNETIC FORCE
Affects electrically charged particles. Responsible for electricity, magnetism, & light;holds e- and p+ in atoms; allows atoms to bond to form molecules. Causes objects to be solid
#EXCHANGE PARTICLE
Particle that carries forces for strong force – gluon, weak force – W and Z bosons, electromagnetic – photon and gravitational – graviton.
#FERMION
Matter particles e.g. proton, neutron and electron. Can be hadrons or leptons
#GLUON
A supposed massless subatomic particle believed to transmit the force binding quarks together in a hadron. They mediate the strong force.
#GRAVITATIONAL FORCE
A force that attracts any object with mass.
#HADRON
A particle made of quarks. Two families: baryons – made of 3 quarks & mesons – made of 1 quark & 1 antiquark. Protons & neutrons are baryons
#HIGGS BOSON
fundamental particle, used by Higgs Field, to interact with other particles two give them m, causes particles to slow therefore cannot reach c due to m.
#LEPTON
Elementary particles, the basic building blocks of matter. Six leptons are in present structure. Varieties are called flavours.
#MESON
Are intermediate mass particles that are made of a quark- antiquark pair. Mesons are bosons and hadrons.
#MUON
A particle similar to the electron, with an electric charge of −1 e and a spin of 1/2, but with a much greater mass. It is classified as a lepton.
#NEUTRINO
A neutral subatomic particle. Mass close to zero. Half-integral spin.Rarely reacts with normal matter. 3 types of neutrino are electron, muon and tau.
#POSITRON
Positron= antielectron =the antiparticle of the electron has an electric charge is +1 e, a spin of 1/2, same mass as an electron.
#QUARK
Quark: a fundamental particle. Quarks combine to form composite particles called hadrons. The most stable hadrons are protons and neutrons.
#SPIN
All particles have spin. Can be up or down & has a fixed value which depends on the type of particle. Particles can be right or left handed
#STANDARD MODEL
Theory concerning electromagnetic, gravitational, strong and weak nuclear interactions and classifying all known subatomic particles.
#STRONG FORCE
Binds quarks together to make subatomic particles e.g.protons and neutrons. Holds together the atomic nucleus. Causes interactions between particles that have quarks.
#WEAK FORCE
A force that plays a role in things falling apart, or decaying.
Mrs Physics was given a tweet to do too. I think she did very well, exactly 140 characters with spaces!
Prof Aidan Robson (Glasgow University)
Hope no one gets to this stage!
It is not as Mrs B said Mrs H’s Bohring Model, but it is more like a Stewart method of remembering the Bohr model!
