The fourth-order maximum for a blue spectral line of wavelength 480 nm480\text{ nm}480 nm is observed at the same angle of diffraction as the third-order maximum for a red spectral line of wavelength λ\lambdaλ.
What is the wavelength λ\lambdaλ?
360 nm360\text{ nm}360 nm
540 nm540\text{ nm}540 nm
640 nm640\text{ nm}640 nm
800 nm800\text{ nm}800 nm
