Your homework questions are attached. Please return to me by Wednesday 20th September.
Higher
higher ODU revision notes
Here are some notes to help you prepare for the assessment later this week. There are also some useful resources on BBC Bitesize.
1996 higher paper
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.
higher particles and waves revision
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.
particle accelerators
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.
Q1(a) Electric fields lines around point charges from mr mackenzie on Vimeo.
Q1b – Electric field between parallel plates from mr mackenzie on Vimeo.
Q2 – Work done in moving a charged particle through a potential difference from mr mackenzie on Vimeo.
Q3 – Calculating the speed of a charged particle in an electric field from mr mackenzie on Vimeo.
quarks, leptons and antimatter
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
Scholar tutorial for ODU unit assessment
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.
Hubble discovers our universe is expanding
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 – nebulae or galaxies? from mr mackenzie on Vimeo.
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 
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.
Hubble’s discovery of the expanding universe from mr mackenzie on Vimeo.
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.
redshift
more redshift
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.
using redshift to map the expanding universe from mr mackenzie on Vimeo.
special relativity
Special relativity is tricky get get your head round. Let’s start with a video about the speed of light.
This video follows Einstein’s thought process as he worked through his special theory of relativity.
time dilation
A Tale of Two Twins from Oliver Luo on Vimeo.
another take on special relativity and the twins paradox
…and the Glesga Physics version
length contraction
This video has helpful examples to explain length contraction.
Sometimes it’s easier to imagine we’re a stationary observer watching a fast moving object go whizzing past. For other situations, it’s better to put yourself into the same frame of reference as the moving object, so that everything else appears to be moving quickly, while you sit still. The muon example in this video shows how an alternative perspective can work to our advantage in Special Relativity.
Another way to think about this alternative frame of reference is that it’s hard to measure distances when you yourself are moving really quickly. Think about it, you’d get tangled up in your measuring tape like an Andrex puppy.
image: trotonline.co.uk
It would be far easier to imagine you’re the one sitting still and all the objects are moving relative to your position, as if your train is stationary and it’s everything outside that’s moving. That keeps everything nice and tidy – including your measuring tape. Got to love Einstein’s postulates of special relativity.
image: mirror.co.uk