ultraviolet radiation

At the beginning of this week, we looked at the physics of ultraviolet radiation.

image courtesy of sonrisaelectrica

The section of the electromagnetic spectrum with wavelengths ranging from 10nm to 400nm is called ultraviolet radiation (uv for short).  Sunlight contains uv rays and it’s those uv rays that are responsible for the suntan you get during the summer holidays.  This Australian animation shows how the ultraviolet in sunlight causes our skin to tan and explains why too much uv will damage our skin.  The SunSmart page has loads of information on staying safe in the sun.

The damage that uv can do to cells is put to good use in some sterilisation equipment, such as this bottle for safe drinking water and the toothbrush sanitiser shown below.

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The Nobel Prize for Medicine was awarded to Niels Rydberg Finsen in 1903 for his research into the effects of ultraviolet on the bacteria that cause tuberculosis.

We used uv banknote checkers in class to view some of the security features built into British banknotes. This image of a Clydesdale Bank £10 note shows part of the pattern that can only be seen under uv light.

 image from Science Photo Library

There is a Bank of England leaflet (pdf) with further information on the security features in our banknotes.

Remember that whenever something glows under a uv light, we’re not seeing the uv radiation itself because our eyes can’t detect ultraviolet.  Instead, we see the fluoresence; visible light given out in response to the uv falling on the material.

Some hair gels fluoresce under uv light.  Here is someone with some of the uv gel in his hair.

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but we don’t see anything until we turn on the uv light.

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Cool, eh?

You can even buy genetically modified tropical fish that glow under uv light.

national 5 exam questions – electricity and energy

Here are the exam-style questions to cover the electricity and energy unit.  I have included a copy of the relationships (equation) sheet and some data tables that you may need to attempt all the questions.  Apologies for the larger file size, it’s due to all the circuit diagrams.

Use the link below to download your own copy.

the challenge of mars

“We choose to go to the Moon in this decade and do the other things, not because they are easy, but because they are hard.” – President John F. Kennedy (12th September, 1962)

It’s 45 years since the success of Apollo 11 and nobody has tried to send a person further away than the Moon.  Why is that?

It turns out there are many challenges to be overcome if we want to send astronauts to another planet, e.g. Mars.  Earlier this year, the BBC Horizon programme looked at the issues.  Here is the episode. I have split the film into three parts.

 

mission to Mars – part1 from mr mackenzie on Vimeo.

mission to Mars – part2 from mr mackenzie on Vimeo.

mission to Mars – part3 from mr mackenzie on Vimeo.

Use the link at the end of this post if you want to download a copy to watch later.