As promised, here are the Scholar notes for unit 2 of the CfE Higher course.
Your assignment will be based on an optoelectronics topic. You will get some ideas for practical work by downloading this booklet.
I have attached a copy of the Scholar notes for unit 3 of the CfE Higher course. You will find background physics with appropriate energy band explanations on pages 103-142.
Don’t print this document, it’s huge!
Thanks to Mr Ferguson for sharing his copy of the marking instructions for the 1996 Higher paper, it’s the only one I didn’t have! You’ll find a link to his answers on the Higher revision page.
Remember that your unit assessment for P&W will take place at the end of this week. The attached notes might be helpful during your revision.
An electric field can be used to accelerate charged particles.
Conservation of energy tells us that
work done by the electric field = change in the particle’s kinetic energy
The speed of the particle can be determined if its charge and the accelerating voltage (potential difference) are known. The notes attached to the end of this post will show how to perform the calculation.
These short video clips show how to draw electric field lines for point charges and parallel plates, with example calculations for the work done by electric fields and the final speed of charged particles in electric fields.
At the end of Our Dynamic Universe, we considered big things like stars, galaxies and the Universe itself. Now the Particles and Waves unit brings us to particles so small we need groups of them just to make a single atom. Is there a connection?
Why do we study particles? from mr mackenzie on Vimeo.
The Standard Model
An elementary (or fundamental) particle is a particle that is not built from other, smaller particles. Until the start of the 20th century, scientists had believed that atoms were elementary particles. However, the discovery of the electron (J.J. Thompson), proton (Rutherford), and neutron (Chadwick), together with Rutherford’s evidence for a heavy, positively charged nucleus at the centre of the atom suggested the atom was not an elementary particle after all.
Brian Cox explains in this video clip…
To go further, we have to introduce some particle physics vocabulary.
These new elementary particles are part of our Standard Model of how the building blocks of the universe interact with one another. The particles that form “matter” are called fermions, after Enrico Fermi (Fermi has an incredibly long list of things named after him). The fermions are divided into two groups; quarks and leptons, as shown in the diagram below.
The Standard Model of Particle Physics. image: The University of Tokyo
The Scholar tutorial is on Monday 14th November, starting at 6pm. You can join the room from 5.30pm using the link on this page.
In the 1920s, Edwin Hubble had access to the Hooker telescope on Mount Wilson, Los Angeles. This was the largest telescope in the world at that time. His first breakthrough was the discovery of a cepheid variable star in the Andromeda nebula. This enabled him to calculate the distance to Andromeda and he quickly realised this was not a nebula but a galaxy outside the Milky Way.
This video follows his work.
Hubble then turned his attention to other galaxies, looking for cepheid variable stars that would allow him to determine their distances from the Milky Way. He used redshift to calculate their recession velocity and plotted a graph against distance.
He found that the recession velocity (v) was directly proportional to distance (d). We can express this relationship as
where is the Hubble constant. Astronomers agree that the current value of the constant is
Since this is a SQA course, we need to convert into SI units – giving
In this video, Professor Jim Al-Khalili looks at Hubble’s work on the expanding universe.
Although he was American, Edwin Hubble transformed himself into a tea drinking, pipe smoking, tweed wearing Englishman during his time as a Rhodes Scholar at Oxford. He probably wouldn’t approve of this last video.
Unfortunately, astronomers were not eligible for the Nobel Prize for Physics. The rules have now been changed.
and Yoker Uni’s video about Doppler and stuff
While redshift can be used to tell us about the recession velocity of (non relativistic) galaxies, we also need to find a way to measure the distance to these galaxies. Astronomers have two main methods to measure these distances; parallax (more parallax here) and cepheid variable stars – there’s a Khan Academy video on cepheid variable stars.