Say we have an elevator moving through deep space at a constant velocity. We have a light emitter at the "top" of the elevator pointing towards a detector at the bottom of the elevator. We shine the light and notice that the frequency at which the light was emitted at the top is the same as that detected at the bottom of the elevator. Now take the exact same scenario only instead of the elevator moving at constant velocity, it is instead being accelerated at a constant 10 m/s^2 in the direction toward the top of the elevator. We now again shine light toward the bottom of the elevator. What is the result? Does the detector at the bottom measure the exact same frequency as the emitter at the top? Or is it blue shifted as it would be in a gravitational field, say if the elevator were simply resting on the ground on the surface of the Earth? My intuition tells me that, in deep space, the frequency would be the same since the top of the elevator and the bottom of the elevator are accelerating in the same direction at the exact same rate, therefore there would be no doppler shift. On the surface of the Earth, however, you would see a small blue shift only because the gravitational effect in the elevator is not uniform, i.e., it is greater nearer the bottom. Is this assessment correct and, if so, does it display an exception to the equivalence principle? Furthermore, would that exception be classified under the "tidal force" category?