If light waves had no amplitude, it would essentially mean that they had no intensity or energy. Amplitude is a measure of the maximum displacement or height of a wave from its equilibrium position. In the case of light waves, it corresponds to the brightness or intensity of the light.
If light waves had no amplitude, they would be completely devoid of energy, which means they would have no effect on the environment or matter. Light waves would become imperceptible to our eyes and would not be able to interact with objects or be detected by any light-sensitive devices, such as cameras or photodetectors.
Without amplitude, light waves would effectively cease to exist as we understand them. Light is a form of electromagnetic radiation, and its ability to interact with matter and carry energy is fundamental to its nature. Removing the amplitude from light waves would eliminate their essential properties and render them non-existent in terms of their physical effects.