Thank you for the opportunity to help you with your question!
its 2. Because you can imagine that in the very small scale of matter, the size of an object may even comparable to wavelength of light. So if the wavelength is too large (visible light) then the light wave cant "catch" the object for us to see.
Please let me know if you need any clarification. I'm always happy to answer your questions.
Nov 15th, 2015
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