How Can Thin Film Interference Cause Complete Destructive Interference?

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Thin film interference can lead to complete destructive interference despite partial transmission and reflection of waves. For this to occur, the two interfering waves must have equal amplitudes, which can be achieved under specific conditions of film thickness and refractive index. One wave reflects off the front surface of the film, while the other is transmitted into the film, reflects off the back surface, and then partially transmits back through the film. The conditions for complete destructive interference are met when these two waves are out of phase and have equal amplitudes. This phenomenon is crucial in applications like anti-reflective coatings and optical devices.
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I've learned that when a wave is partially transmitted and partially reflected, it loses some of it's amplitude in order to conserve energy. How then, in thin film interference, can one wave produce complete destructive interference with the other if it has been partially transmitted? Wouldn't the two waves have different amplitudes?
 
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For complete destructive interference, the two waves need to have equal amplitudes. Such complete destructive interference can happen in the reflected light when a thin film of appropriate thickness and refractive index covers a substrate. One ray is reflected directly from the front surface of the film. The remaining light is transmitted into the layer, and partly reflected at the back surface. This ray travels back, and partially transmitted at the film-air interface. This ray interferes with the first one.

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