To solve this problem it is necessary to apply the concepts related to the concept of overlap and constructive interference.
For this purpose we have that the constructive interference in waves can be expressed under the function

Where
a = Width of the slit
d = Distance of slit to screen
m = Number of order which represent the number of repetition of the spectrum
Angle between incident rays and scatter planes
At the same time the distance on the screen from the central point, would be

Where y = Represents the distance on the screen from the central point
PART A ) From the previous equation if we arrange to find the angle we have that



PART B) Equation both equations we have


Re-arrange to find a,


You may confuse two minerals by their colors so using streak is another way for showing their "true colors "
The answer is the less dense plate slides over the denser plate.
question one b
question 2 i think a
3 d
4 c
5 not sure but wanting to say d
6 letter b
7 not sure
8 idk
9 i have no idea