Here is the practice NAB for unit 1. I will post the answers on Sunday morning. I suggest you work thourgh the unit 1 revision materials before attempting this assessment.
Don’t cheat! Do the NAB before looking at the answers.
podcast
podcasts go in this category for the feed to iTunes
higher – lasers
The first laser was demonstrated in 1960 by Theodore Maiman and his research group at Hughes Aircraft Corporation† in California. Here is a good background article on the first laser, its inventor and the role that Einstein played in developing the theory of stimulated emission.
The principle of laser operation is outlined in this description of Maiman’s laser, which used a rod of polished ruby inside a spiral flashtube.
My favourite James Bond film, Goldfinger, has a scene where Sean Connery (the best 007 imho) is strapped to a table under a huge red laser. It should have been a saw but the invention of the laser, just 4 years earlier, was a gift for the writers. This scene helped the film win the best effects Oscar in 1965 and, more importantly, gave us the ultimate Bond quote:
Bond: Do you expect me to talk?
Goldfinger: No, Mr. Bond, I expect you to die.
Everyone should watch the laser scene.
Bonus points if you can tell me about the bad physics in that clip…
You can try running a laser for yourself. Click on the picture below to load a simulator. You’ll need Java on your computer to run the simulation.
Try changing lamp (pump) irradiance and mirror reflectivity on the single atom version before moving on to the multiple atom tab.
There are some pdf notes on lasers attached to the end of this post.
† Disclaimer: I used to work for Hughes before I trained as a physics teacher – the Glenrothes branch, not California 🙁
higher – line spectra
We’ve looked at line spectra with spectroscopes and a spectrometer recently. Now we’re considering how these different colours of light are produced.
Here is a website that lets you choose the energy of a photon and see whether or not it causes a change in the energy of an electron inside the hydrogen atom. Try it – the labels under the slider for photon energy match the electron transitions.
You can read more about line spectra and their origin here.
The visible line spectrum of the Hydrogen atom is explained in this short animation. Click on the image below to start the clip.
While you’re watching the clip, try to explain why the video does not include ANY of the possible transistions back down to the ground state.
I’ve attached a pdf file with further notes on line spectra and the absorption/emission of photons. Click on the link below to download your copy.
Higher – photoelectric effect
We looked at the photoelectric effect earlier this week. This video has a similar demonstration to the gold leaf electroscope experiment I showed you in class and includes an explanation of the process.
Click on the picture below to download the simulation we used to investigate the effect of irradiance on frequency on photocurrent. You’ll be prompted to install Java if you don’t have it already.
Once the animation is running, you can;
- change the metal under investigation (we used zinc in class)
- vary the wavelength of the incident light
- vary the irradiance of the incident light.
Notice that below the theshold frequency you can’t get any photoelectrons, even if you set the light to its brightest setting.
Compare your results to the graphs provided in your notes.
I have attached some notes & questions on the photoelectric effect. Click on the link below to download a copy.
national 5 – satellites
We’ve started looking at telescopes and this BBC programme from 2 years ago featured the replacement for Hubble, the James Webb Space Telescope. The presenter, Maggie Aderin Pocock now hosts The Sky at Night on BBC4.
Please take some time to watch both parts of the film. Maggie covers the basic idea of satellites, how we achieve geostationary orbit, looks at examples of Earth observation and the manufacture of the James Webb’s massive 6.5m mirror. In part 1, around 17 minutes in, you’ll see satellite footage over the Highlands, can’t quite see Thurso though.
Satellites-part1 from mr mackenzie on Vimeo.
Satellites-part2 from mr mackenzie on Vimeo.
If you want to download a copy of the video to watch later, use the download link below. Please be patient, the file is about 660MB in size.
Higher unit 2 – solutions to practice NAB.
Here are my solutions to the practice NAB for Higher unit 2.
Check your own answers carefully. Did you;
- mix up the equation for charged particles with those for capacitors?
- remember to calculate the period of an ac signal in seconds?
- make the correct substitutions for V1 and V2 in the differential amplifier question?
- use “it” instead of nouns in your explanations?
practice NAB for Higher unit 2
Try this practice NAB if you are studying for a unit 2 resit next week. I’ll post answers over the weekend.
AH Physics: wave-particle duality
We’ve been looking at wave-particle duality this week.
Here are 2 videos. The first is about electron diffraction (G. Thomson’s experiment) and De Broglie’s equation, while the second looks at the Davisson-Germer experiment.
Following on from our discussion of the Davisson-Germer experiment, I found a copy of Davisson’s Nobel Lecture online. You can read it using the download link below. You should be able to follow Davisson’s lecture as it ties in nicely with the modern physics element of the AH course.
AH homework solutions
Sorry for the long wait! Here are worked solutions to the homework questions on calculus and special relativity. Come and see me if you want to go over any of them. Thanks.
Using Excel for your LO3 and Investigation
We’ll spend the next two lessons in the library learning how to use Excel. Download the instructions using the link below. If you have your own LO3 data, feel free to work with those values instead of the numbers I have provided.
By the end of this activity you will be able to;
- manipulate raw data using formulae in cells
- plot a graph of your results
- add error bars to your graph
- add a line of best fit
- calculate the gradient and y-axis intercept of your line