mrmackenzie

How a TV set works – part 3

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The site I have been using throughout the television section of the course is here.

The shadow mask makes sure that electrons fired from the filament responsible for each colour of sub-pixel do not hit the wrong phosphor dots, e.g. electrons sent by the “green” gun do not reach the phosphor dots that glow red or blue. This animation shows how the shadow mask works.

 

Remember: electrons do not have a colour.  Colour is only produced when electrons collide with phosphor paint.

How a TV set works – part 1

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Here is a short video clip showing how an image can be built up on a TV screen, one line at a time. In a real TV set, the beam moves much more quickly (about 7000 m/s!) across the screen and 25 complete images are shown each second.

raster scan from mr mackenzie on Vimeo.

Remember that in a real TV set, the beam does not scan its way back up the screen but takes a “flyback” from the bottom right to the top left corner to start on the next image.

site maintenance

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I am moving this site to a new hosting company during the holidays.  You might notice some broken links or missing videos.  Please let me know by leaving a comment so I can fix anything I have missed.

Past papers are currently unavailable on the AH, Higher & Int2 pages.  Some (not all) can be found by typing “pastpaper” in the search box at the top of the page.

Thanks.

decommissioning Dounreay – Bang Goes the Theory

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This week’s episode of Band Goes the Theory was about the Fukushima disaster in Japan.  Part of the programme was filmed at Dounreay, where Dallas investigated the methods being used to decontaminate the site.  You can watch the part about Dounreay by playing this clip.

The whole programme is available for download using the link below (large download).

Podcast Video [ 29:04 ] Download (1127)

AH – help using Excel

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This tutorial will help you with adding a line of best fit to your LO3 graph.  If you use the linest function, you can extract useful information on gradient and intercept of the line.  There are also screenshots to show how error bars can be added to individual points.

Excel Tutorial: Using LINEST function, Plotting a graph, Adding Error Bars

I have added a download link to a short pdf on the use of linest.

 

eBook Download (1896)

AH LO3

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You completed the practical aspect of your LO3 task today.

For next week, please process your data so you can show me

  • complete table of results
  • a graph of centripetal force vs the square of angular velocity
  • sample calculations for your uncertainties.

This will probably be easier to complete if you use a spreadsheet program such as Excel or OpenOffice.  You will need diagrams for the procedure section of your LO3 report.  Scanned images of the apparatus are available here.