"With naked eyes" vs. "With the naked eyes" [closed]

Solution 1:

The idiom is the naked eye:

noun

(usually the naked eye)
Unassisted vision, without a telescope, microscope, or other device:
threadworm eggs are so small that they cannot be seen with the naked eye

_{ODO Emphasis added}

Solution 2:

ScotM's answer is great. To address your clarified questions:

• "You can see it with naked eye" is (2. incorrect)
• "You can see it with naked eyes" (2. incorrect) - possibly acceptable in a poetic usage, but otherwise awkward
• "You can see it with the naked eye" (1. correct)
• "You can see it with the naked eyes" (2. incorrect)
• Some of the above 4 sentences might be undesirable but have the same meaning (2. no)

Solution 3:

The previous two answers are both correct, but I'd like to add that if I were using it in an informal setting, such as a science brochure for children, I'd say "You can see it with your naked eyes," keeping the pronouns consistent. "The" naked eye implies a more formal style, in which case I would forgo the "you" and say instead, "it can be seen with the naked eye" or "one can see it with the naked eye."