[Year 12 IPM] Exam Post Mortem now online

[Mark Scott]

Mike
 
Are you really suggesting that they expected an answer like yours from the sheltered workshops we call IPM classes?
 
Mark Scott
Luther College

________________________________

From: ipm-bounces at edulists.com.au on behalf of Mike Brookes
Sent: Thu 10/11/2005 7:36 PM
To: Year 12 Information Technology Processing and Management Teachers'Mailing List
Subject: Re: [Year 12 IPM] Exam Post Mortem now online




Carping:
Q3) The method used to store data on a DVD RW is not pits in an
Aluminium substrate - that's the method used to store data on mass
produced Cds and DVDs that are read only.

DVD RW disks use a polycrystalline layer (usually an alloy of Silver,
Indium, Antimony and Tellurium). In the normal ordered crystalline state
the layer is shiny and reflects a low powered laser.

When the alloy is hit with a short high power laser burst the alloy
melts (500 -700 degrees) then cools down quickly so that it forms an
irregular mass of tiny crystals rather than the ordered crystalline
form. This irregular form has a low reflectivity and scatters the low
powered laser used to read the disk.

To erase the data the laser is used at medium power to heat the alloy to
above the re-crystallisation temperature but below the melting point
(around 200 degrees) for a sufficient time to allow the alloy to
crystallise back into its shiny form.

Once upon a time in a galaxy far, far away IPM was a subsection of
Information TECHNOLOGY - 'tis great to see a question which actually
requires the students to know a bit about technology instead of being a
glorified business management course. :-P

PS difficult to see how the question could be interpreted as how would
the end user store data on these devices as you would use the same
answer for all three - eg. drag the file icon to the icon representing
the device/directory.



Mike Brookes
Chief cook and bottlewasher
Copperfield College

Mark Kelly wrote:
> My annual whinge is now online at
>
> http://www.mckinnonsc.vic.edu.au/la/it/ipmnotes/exam/2005exam/index.htm
>
> Feel free to carp, bicker and protest.
>
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