Question

Which of the following light can penetrate deepest in the ocean water?

• A. Red
• B. Blue
• C. Green
• D. Yellow

Hint:

Remember the absorption order: Red is absorbed first (shallowest), and Blue is absorbed last (deepest).
This explains why many deep-sea animals are red, as they appear black and invisible in the blue-dominated deep waters.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Solar radiation entering the ocean is absorbed and scattered by water molecules, dissolved organic matter, and suspended plankton.
This selective absorption of different wavelengths determines the depth to which different colors of light can penetrate, shaping the photic zone.

Step 2: Detailed Explanation:
When sunlight enters clear ocean water, different wavelengths of the visible spectrum are absorbed at different depths:
Red light, which has longer wavelengths and lower energy, is absorbed within the first 5 to 10 meters of depth.
Yellow and orange wavelengths are absorbed within the top 20 to 50 meters.
Green and blue light, having shorter wavelengths and higher energy, are scattered less by pure water molecules and are not easily absorbed.
In clear, oligotrophic open-ocean waters, blue light penetrates the deepest, reaching depths of up to 200 meters or more.
This is why clean ocean water appears blue, as the blue wavelengths are scattered back to our eyes while other colors are absorbed.
In turbid or highly productive coastal waters containing dissolved organic matter (gelbstoff) and phytoplankton, green light may penetrate deeper than blue because chlorophyll absorbs blue light.
However, as a general rule for typical clear ocean waters, blue light penetrates the deepest.

Step 3: Final Answer:
Blue light can penetrate the deepest in ocean water.