Final answer:
A deposited layer of evaporated tungsten on an x-ray tube window may lead to decreased x-ray output and reduced tube life due to the increased thermal stress on the apparatus. Therefore, the correct answer is 1) Decreased x-ray output.
Step-by-step explanation:
An older x-ray tube with evaporated tungsten deposited on the tube window may lead to specific changes in the functioning and lifespan of the apparatus.
Tungsten is used in x-ray tubes because its high melting point can accommodate the high energy and temperature resulting from the striking electrons that produce x-ray photons.
When the tungsten from the anode evaporates and deposits on the tube window, it can attenuate the x-ray beam, which would result in decreased x-ray output.
Additionally, the coating of the tube window leads to a decreased efficiency of x-ray photon production and contributes to the generation of additional heat, potentially reducing the tube life due to the extra thermal stress on the system.