Since all the cells are still tucked safely away in their beds, I played around with taking images of light bulbs. A standard incandescent bulb is fairly easy to take an image of: . This is actually two images added together, one taken of the unlit bulb and the other of the lit bulb.

More interesting is an arc lamp. Arc lamps are used in many applications- fluorescent lights are low-pressure versions of arc lamps. We have a high-pressure Mercury arc lamp used for fluorescence imaging. Here’s an image of the unlit arc: .

The gap between electrodes is about 1 mm. A high voltage pulse is sent across the electrodes, creating a spark. This ionizes and heats up various gases present in the bulb, which then heat up a small amount of Mercury (about 100 micrograms). These images show the process of lighting an arc- if you look carefully, you can see the bits of Mercury pool together and evaporate. After the bulb was lit for a few minutes, I took an image of the hot electrodes. I have never seen images like this before.

Don’t try this at home- the arc lamp gives off a lot of ultraviolet light.

As I said above, arc lamps are related to fluorescent lamps. Here’s an image of the germicidal bulb we use in the culture hood to sterilize the space: .

Last are some images of a HeNe laser- lasers also operate on the principle of fluorescence. I’ve always marveled that the most common (pre solid state) laser is also perhaps the most difficult to understand- collisions of the Ne and He atoms are required to generate lasing. A image of the entire insides isn’t too interesting, so here are some higher-magnification images of some of the bends in the various glass envelope. You should be able to see where the lasing occurs (as opposed to the sub-threshold fluorescence) in the thin capillary: the color of the light changes as well.

One final caveat: I’m red-green color blind, so these images most likely look rather garish to you. They look very well-balanced to me, a soft red glow going into a strong magenta in the laser cavity.