Answer:
a) 7.947 radians
b) 
Explanation:
y = Distance from central bright fringe = 2.5 mm
λ = Wavelength = 600 nm
L = Distance between screen and source = 2.8 m
d = Slit distance = 0.85 mm


a) Phase difference

∴ Phase difference between the two interfering waves on a screen at a point 2.50 mm from the central bright fringe is 7.947 radians
b) 
∴ Ratio of the intensity at this point to the intensity at the center of a bright fringe 
Answer:
No distance is the length between two routes
Explanation:
Distance is the length of the route between two points. ... Direction is just as important as distance in describing motion. A vector is a quantity that has both size and direction. It can be used to represent the distance and direction of motion.
I don’t think I understand the question but true?