No one in Physics is helping,Can someone help me with physics over here?

Question

dani_rose · Answer

What's your question?

sophadof · Answer

The distance between two slits in a double-slit interference experiment is 2.1 ´ 10–3 mm. A first-order bright fringe is detected at an angle of 17.0° from the central maximum.
a) What is the wavelength of the light?
b) Is this light visible to humans?  If so, what color would it be?

sophadof · Answer

@Dani_Rose

dani_rose · Answer

I have no idea sorry

zale101 · Answer

What is the formula for the wavelength of light?

zale101 · Answer

There is a formula for it. Do you remember it?

sophadof · Answer

C=weird A thing*f @Zale101 
I don't know the a thing and what it's called

zale101 · Answer

I read the questions wrong. I apologize So your question is requiring you to know this information
nλ = dx/L
Where:
n = Number (order) of anti node 
λ = Wave length (m)
d = Distance between slits (m)
x = Distance between n =0 and n = 1 anti node (m)
L = Length from diffraction grating to screen (m)