double slit and light intensity question?

Question

I have 2 questions.

1.) The light intensity on a screen behind a double slit is shown, in which y = 1.7 cm. The slit spacing is 0.20 mm and the wavelength of the light is 570 nm. What is the distance from the slits to the screen?

The graph peaks in the middle at 12 mW/m^2 and is 0 at each end.

2.) In a double-slit experiment, the slit separation is 195 times the wavelength of the light. What is the angular separation between two adjacent bright fringes?

I have no clue what to do. If anyone can help thanks.

Answer 1

I'll assume y is the separation of projected maxima or distance from center to the 1st maximum.
Screen distance D is related to y, wavelength λ, and slit separation d by y ≈ λD/d (see ref.), so D ≈ dy/λ (ans. 1).
theta ≈ y/D ≈ λ/d
if d = 195λ, then theta ≈ 1/195 rad (ans. 2).

Answer 2

a) use the equation Ym=[D(wavelength)] /d

Ym is distance from central maximum to minimum of order m=1, or where the light is brightest (most intense) to darkest (least intense)

D is distance from slits to where the frequency is being detected.

d is distance between slits