Step 23: Radiography: X-Ray Cassettes
X-Rays are invisible, much like infrared light. Unlike infrared light though, they are very energetic and are more than capable of exciting atoms, possibly a whole bunch of them. What do you get when you have excited atoms?
Photons! Lower energy photons, ones which we can see. We can use this property, 'X-Ray Fluorescence' to convert an x-ray beam into visible light, allowing us to witness the information contained within it. Often times, this is done with something called an 'intensifying screen'; a plastic sheet impregnated with an x-ray responsive phosphor.
Intensifying screens are contained in intensifying cassettes; little light tight folders which house x-ray film. [Image 1] ought to give you a good idea of what these things look like.
Types of Cassettes
Like many things in this world intensifying cassettes come in many flavors. Blue, Green, Rapid, Ultra Rapid, Normal...
'Ultra Rapid' screens will give you the brightest images, and thus shortest exposure times. This is not without its downfalls though. In order to appear bright, the crystals in these screens must be very large; large enough that the resulting image is a bit blurry.
'Regular' screens will likewise produce a sharper image, albeit a dimmer one. More x-rays and longer exposure times would then be needed, but this is the price we pay.
'Fine' cassettes will produce a very sharp image. Unfortunately it's also a very dim image...