Laboratory Safety
Physics 3340/4430/5430 Spring Semester, 2006
The first thing you should be
concerned about in the lab is the safety of yourself and your fellow students.
There are a number of potentially serious hazards in this lab, but if you are aware
of the dangers and use sensible precautions, you will be quite safe.
Electrocution is by far the most
serious hazard. You will be working continually with electrical equipment,
which often uses high voltages. You should always be aware when you are working
near exposed wires, and whenever you are changing high voltage electrical
connections always double check that the power is turned off, and any
capacitors, either inside the power supply or outside, are discharged. One of
the primary dangers of working with high voltages is that you do not have to
actually touch a wire to be shocked‑ the current can arc to your body
even if you are a few mm away. A good standard practice when working with
exposed high voltage is to always keep one hand in your pocket to avoid the
possibility of a current entering your body through one hand and leaving
through the other, because it is closest to ground. The reason this is
particularly bad is that the current will pass through your heart and start it
fibrillating. Most accidental electrocutions are due to fibrillation. For this
reason the most lethal voltage levels are around 400-500 V, since this is most
likely to lead to currents which cause fibrillation. Higher voltages (for
example, 2000 V), while still dangerous, tend to cause the heart muscle to
simply spasm, but beating will usually resume if the voltage is removed
quickly. High voltage, high current sparks frequently cause very deep burns
which take a long time to heal. The 120 V line power is relatively safe, but
still can provide painful shocks and can be quite dangerous if your body is a
relatively low resistance path, for example if your hands are wet when you
touch the wire. Voltages below 50 V usually involve little danger.
In this lab you may work with a
variety of radioactive sources. The textbook by Melissinos (pg. 137, copies are
in the lab and on reserve in the library) has a section on radiation safety,
which you should read before you use any of these sources. Most of them are
relatively weak and involve little danger if you exercise minimal precautions.
If you have any question about the amount of radiation near a source, there are
Geiger counters in the lab, and you are encouraged to use them to measure the
amount of radiation. This will show you which regions of the sample you may
want to avoid extended contact. The only significant danger from the sources
in this lab arises if you ingest (eat or swallow) them. You will probably
not intentionally eat any of the radioactive sources, but there is a small
possibility that one of the seals may leak and this could contaminate something
that you eat. Thus you should wash your hands after handling any radioactive
source, and eating or drinking of any food in the 3340/4430/5430 lab area is
strictly forbidden. Before using any radioactive sources you must check with an
instructor to be sure that you known how to handle them properly, and how to
sign-out and return them according to procedure.
The last potential danger in the lab is eye damage from low power infrared and helium neon lasers. These lasers have low enough power that the danger is rather small, but you still need to be careful to insure that you do not allow the direct laser beam to enter your eye, or the eye of a fellow student. This means you should be careful to keep track of where the laser beams are going when you reflect them off of optical components, and you want to be careful to avoid sending any beams at eye level, or putting your eye down at the level of the beams. A particular concern with the He‑Ne lasers is that there is a few second time delay between when you turn the on switch and when the laser light comes out. If the light does not come out immediately, DO NOT PUT YOUR EYE DOWN TO LOOK INTO THE HOLE FROM WHICH THE LASER LIGHT COMES OUT!!