Final answer:
The power of the tear layer for a person with a 0.750 D prescription cannot be determined without additional information, as standard prescriptions account for the lens's total power, typically not distinguishing from the tear layer's negligible power.
Step-by-step explanation:
The power of the tear layer for a mildly farsighted person with a contact lens prescription of 0.750 D and a near point of 29.0 cm is not explicitly provided by the question and cannot be directly calculated without additional information. When the eyes are relaxed and in the state of least accommodation, they are focused at a distance. For a farsighted person, the near point is farther away than normal, which means without corrective lenses, the person cannot see clearly at normal reading distances. To correct for hyperopia (farsightedness), converging lenses are used, and the power of these lenses is positive. The power of the tear layer, when considered in an ideal correction scenario, is assumed to be part of the overall correction that the contact lenses provide since they sit directly on the cornea with the tear layer in between.
If a prescription is given, it generally includes the correction needed for the lens itself, which should already consider the power of the tear film unless specific measurements are taken to separate the two. That said, in practice, it's difficult to measure the power of the tear film separate from the lens because it's a very thin fluid layer and has a negligible optical power compared to the lens. Therefore, unless the problem provides additional data or there's a specific method to measure the tear layer's power, it's typically not distinguished from the lens's power in prescriptions.