[neilep (OP)]

Darlings,

Gosh ewe are such a klevur lot !...we are all so grateful for this wonderful resource !..thanks for sharing your wisdom's !

As a sheepy, I of course am photoelectric !...shine a torch on my ears and my Joy Dept lights up !..LOL !..makes hiding in Christmas Trees very easy !..ewe know it makes sense !

Photocells are great aren't they ?

Look here's one :

 [ Invalid Attachment ]

Nice eh ?  that's one fine sexy looking cell right there !!..oh my giddy aunt !!

How does one regulate the amount of light a photocell absorbs ?..can too much light be harmful ?..could a depressed photocell with suicidal proclivities end it all by standing in front of floodlight for a long time ? (it happens ewe know !)

Ewe see.....i want to know....cos..well..I don't know and ewe know and I want ewe to make me know too.

will ewe ?

awwwwww thanks !! (hugs the forum) *le affectionate*


hugs & shmishes


mwah mwah mnwah !!



Neil
A Photo Of A Cell !! [ Invalid Attachment ]

[lyner]

Do you mean"can you 'roast one'?"?
Most semiconductor devices can operate at 100C+.
The sensitivity could be altered if you changed the operating temperature significantly but the totally energy absorbed per m squ is a lot less than 1kW on the Earth's surface. Not a serious prob, I think.
If you want to "regulate" how much is absorbed, you'd have to use a nice little sunshade or sunnink.
Mwaah

[neilep (OP)]

Do you mean"can you 'roast one'?"?
Most semiconductor devices can operate at 100C+.
The sensitivity could be altered if you changed the operating temperature significantly but the totally energy absorbed per m squ is a lot less than 1kW on the Earth's surface. Not a serious prob, I think.
If you want to "regulate" how much is absorbed, you'd have to use a nice little sunshade or sunnink.
Mwaah

Why Thanks Ewe Mr Sophiecentaur sir. This is great info. I was kind of referring to though the intensity of light.

If I shone a very very bright light upon it, brighter than it is designed to absorb....does the extraneous light cause damage ?....what determines the intensity of light it can absorb ?

[LeeE]

That looks like a photo-resistor, so while it would be unlikely to break due to the light being too bright, putting too high a PD across it, or drawing too much current through it might damage it.  Both scenarios would be unlikely in practice though.

[Bored chemist]

That light sensor does, indeed, look like a photoresistor and they are fairly robust. Photodiodes are pertty well able to look after themselves too. But if you expose a photomultiplier to anything like normal light levels while it is switched on you will kill it. On the other hand, they do let you count photons one at a time.
http://en.wikipedia.org/wiki/Photomultiplier

[lyner]

I wonder what "over exitation", as a destruction mechanism, means in that wiki link.
If the current from the cathode is limited by the power supply, I don't see what could damage the tube. You could burn out the anode - or a dynode if the current were too high, of course.
My very first proper paid work was to make a resistive voltage divider chain for a photomultiplier in a film scanner. Ahhhh.

[LeeE]

Is there a risk of burning out the display phosphor?

[lyner]

I don't think so (it's the opposite of a phosphor, actually- light produces electrons).
The statement about possible damage stipulates "when the device is turned on", so the photocathode is, presumable, robust.That's not to say the photocathode couldn't be temporarily charged in the presence of a bright light.

[neilep (OP)]

That looks like a photo-resistor, so while it would be unlikely to break due to the light being too bright, putting too high a PD across it, or drawing too much current through it might damage it.  Both scenarios would be unlikely in practice though.

Thanks LeeE. oops, did I get my resistors and cells mixed up ?..sorry about that !...but thanks for the info.

[neilep (OP)]

That light sensor does, indeed, look like a photoresistor and they are fairly robust. Photodiodes are pertty well able to look after themselves too. But if you expose a photomultiplier to anything like normal light levels while it is switched on you will kill it. On the other hand, they do let you count photons one at a time.
http://en.wikipedia.org/wiki/Photomultiplier

ooh..very fabo link..thanks for interesting info BoredChemist. I think I may have discovered a new hobby in counting photons !
So, a photomultiplier can come to harm if exposed to too much light ie: intensity !..thanks,

[techmind]

Look here's one :

 [ Invalid Attachment ]

The device pictured indeed looks like a photoresistor. Often made from CdS (cadmium sulphide). I believe you can get drifts in sensitivity if you expose such devices to full sunlight for prolonged periods... but in typical uses this isn't enough to be particularly problematic.

With the exception of photomultiplier tubes, full sunlight on common light-sensors isn't usually much of an issue, unless you're trying to do very accurate measurements. Sensors for metrology will normally be kept in the dark to minimise long-term drift between calibrations.