Answer to Question #114345 in Physics for James

Question

Assume the human eyes can detect wavelengths from 380 nm to 900 nm (near infrared region). Do the first order and second order overlap?

Answer 1

It is a bit unclear what the first and second order mean, but a human eye can detect wavelength up to 700 nm. In this case, the visible part of electromagnetic spectrum overlaps the infrared part of the spectrum. One research shows that in some conditions, people can detect infrared light. See https://www.pnas.org/content/early/2014/11/25/1410162111 for more information.