Final answer:
In a darkroom, to check for light leaks, leave a penny on the X-Ray film for at least five minutes and then develop the film to check for a clear penny image.
Step-by-step explanation:
When checking for light leaks in the darkroom, especially related to X-Ray film, it's crucial to ensure the integrity of the film is not compromised. The correct procedure would be to leave a penny on the X-Ray film for at least five minutes in a completely darkened room. After this period, if the film is developed and a clear image of the penny appears, it indicates that light has not affected that area of the film, thereby confirming that the darkroom is free of light leaks.