Is it true that turning the gauge off completely stops the radiation?

Turning the gauge off does not completely stop the emission of radiation. When a nuclear gauge is turned off, it may still emit a small amount of radiation because the radioactive source remains intact and could continue to decay. The process of radioactive decay is constant and does not cease simply by switching the device off.

This means that while the gauge's function as a measuring device is halted, the underlying radiation source is still present. Therefore, the correct understanding is that turning the gauge off does not eliminate radiation; it only reduces the gauge’s operational function. This aligns with the chosen answer, emphasizing the persistent nature of radiation emitted from the source itself, irrespective of the operational state of the device.