Final answer:
Neglecting reflection and absorption, 100% of the light from a source beneath the water's surface emerges out, because all the light that reaches the surface will be refracted into the air.
Step-by-step explanation:
The percentage of light that emerges out of the water's surface, when a small source of light is placed at some depth beneath it, is dependent on several phenomena including refraction and reflection. However, the question specifies that reflection from the bottom and absorption by water are to be neglected. In this case, the light that hits the surface will undergo refraction according to Snell's law. Given the absence of any losses due to absorption or reflection, essentially all the light that reaches the surface will pass through into the air above. Therefore, the percentage of light emerging out of the surface of the water in the given scenario would be 100%.
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