Diffraction Grating - all visible light?

[clamatoman]

Homework Statement

Find the smallest grating spacing that let's you see the entire visible spectrum.
400nm to 700nm comprises the visible light spectrum.
no other information is given.

Homework Equations

nλ=d sin θ

The Attempt at a Solution

I am not sure how to start as all i have been given is a spectrum of wavelengths...?

 

[clamatoman]

Well, apparently its 700nm. And 1400 nm for the second order.

 

[lychette]

What is the maximum angle where a wavelength can be observed?