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By mrmackenzie, March 23, 2010 10:43 am

We’ve been looking at interference recently.  I found two nice simulations that you might want to try running at home to confirm your understanding of things like;

• relationship between fringe spacing in the pattern & wavelength
• location of the 0, 1st, 2nd order fringes
• what happens when the screen is moved towards/away from the 2 slits/sources

The first simulation is based on the interference of sound waves and is similar to the experiment we set up last week in class.  Click on the image below to start the simulation, you will need Java for this to work.  Make sure you choose the two source interference tab as shown in the picture.

The second simulation can be run as sound, light or water waves.  I selected the light option for this screenshot.  Click on it to run the simulation.  You are free to run 2 sources or one source with a double slit barrier and adjust the amplitude and wavelength.

The view screen option is nice as it shows what the fringes would look like.  You can also display a plot of light intensity (irradiance).

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By mrmackenzie, March 20, 2010 12:11 pm

one less tv by Kevin Steele
Attribution-NonCommercial License

I showed you a handy site that explains nicely how all the parts of a TV set come together to produce a “moving image” on your screen. You can visit the site yourself by clicking here.

The site covers

• pixels
• brightness control
• moving the spot around the screen to produce an image
• displaying many separate images per second

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By mrmackenzie, March 16, 2010 7:57 pm

Today we looked at the way in which a tv set produces a picture.  We used the Maltese cross tube to produce the effect shown in this photograph.

• Can you explain why there are two shadows of the Maltese cross on the screen?
• What evidence can you remember from the lesson to justify your explanation?

Then we moved on to the Perrin tube.  This allowed us to scan the electron beam across the painted end of the tube using the magnetic field of two Helmholtz coils.  Here is the video clip we recorded at the time.

raster scan from mr mackenzie on Vimeo.

• Why is the scanning pattern shown in this video different from the scan used in a tv set?

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