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# Continuous spectrum watch

1. What does "hot things emit a continuous spectrum in the visible and infrared" mean and also is this only for matals?
2. (Original post by Jennifer50)
What does "hot things emit a continuous spectrum in the visible and infrared" mean and also is this only for matals?
it just means 'without gaps'... and it applies to all matter.

someone asked a related question http://www.thestudentroom.co.uk/show...php?p=62071773

The gaps you can see in the sun's spectrum are because the light from the sun has passed through the sun's atmosphere and the earth's atmosphere and some frequencies of light have been absorbed by atoms on the journey.
3. So if it's all matter can it be a hot metal or a hot orange for example or hot plastic?
4. (Original post by Jennifer50)
So if it's all matter can it be a hot metal or a hot orange for example or hot plastic?
in principle - don't suppose the orange would be very appetising afterwards though.
5. The bit that is confusing me is what it means by in the "visible and infrared". What does this mean?
6. (Original post by Jennifer50)
The bit that is confusing me is what it means by in the "visible and infrared". What does this mean?
infra red is the same 'stuff' as light - they are both electromagnetic radiation.

the difference is that only a part of the electromagnetic spectrum is visible - IR is the radiation that's just too low in frequency to be visible.

7. So it just means the continuous spectrum and infrared radiation? Does this include uv radiation?
8. (Original post by Jennifer50)
So it just means the continuous spectrum and infrared radiation? Does this include uv radiation?
the infrared IS part of the continuous spectrum, it's just outside the range you can see.

at any temperature there's an upper limit to the frequency that can be radiated - the sun has an effective temperature of about 4500 K and radiates ultraviolet... filament lightbulbs have a temperature of about 3000K and don't radiate ultraviolet
9. So is uv part of the continuous spectrum and only sometimes emitted whereas infared is always emitted?
10. (Original post by Jennifer50)
So is uv part of the continuous spectrum and only sometimes emitted whereas infared is always emitted?
you only get UV if the temperature is high enough... here's a simulator, maybe playing with the temperature slider will make it clearer.

http://highered.mheducation.com/olcw...%20Interactive

note it autoscales the intensity - you still get some infrared at the highest temperatures.
11. (Original post by Jennifer50)
What does "hot things emit a continuous spectrum in the visible and infrared" mean and also is this only for matals?

It is for all hot objects. even people (we are above absolute zero)

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