Final answer:
The safe light coin test is a procedure used to check if a safe light can expose photosensitive material without causing unwanted exposure, indicated by the appearance of the coin's image after the material is developed.
Step-by-step explanation:
A safe light coin test is performed by placing a coin on a piece of photosensitive material and exposing it to a safe light. The objective is to determine if the light is safe for use with sensitive materials without causing any unwanted exposure. First, the material is placed in a completely dark environment. After setting a timer, the coin is placed on the material and exposed to the safe light for a specific period of time.
Once time elapses, the coin is removed, and the photosensitive material is developed. If an image of the coin appears, the safe light is not adequate as it has caused exposure. The test is derived from darkroom procedures where photographers need to ensure that their lighting does not affect photographic films and papers. The safe light test is an easy and effective way to confirm the safety of the lighting conditions for developing photos without the risk of ruining the sensitive materials.