The answer is B. P waves.
I took the test and it was correct. I hope this helps!
Answer:
Width of the slit will be equal to 1.47 mm
Explanation:
We have given wavelength of the light 
Distance D = 8 m
Distance between first minimum dark fringe and the central maximum is 2 mm
So 
We have to find the width of the slit
For the first order wavelength is equal to
, here a width of slit
So 
So width of the slit will be equal to 1.47 mm
That's up to you because you have to go through the book to see their expressions
Answer: 117.8 nm
Explanation:
Given,
Nonreflective coating refractive index : n = 1.21
Index of refraction:
= 1.52
Wave length of light = λ = 570 nm = 


Hence, the minimum thickness of the coating that will accomplish= 117.8 nm