10 points: A few light/wave questions?

Question

I) Find the wavelength of light in the following scenario: Monochromatic light hits two slits 0.5 mm apart. Successive nodal points on a screen 4 m away are 4.5 cm apart close to the center of the pattern.

II) Find the separation between 2 slits where 700 nm orange light has its first max. at a angle of 5 degrees

III) A beam with a wavelength of 500nm falls on one slit producing a central maximum 4.5 cm wide on a screen 1.5 m away. Find the slit width.

Thanks in advance for your help =) I really need the answers to check against, since my worksheet doesn't supply solutions.

Answer 1

1.)   h = xd/L = .005*.045/4 = 56.2 um

2.) etc... etcc...