Answer:
Angle of ray makes with the vertical is 62.1 degree
Explanation:
As per the ray diagram we know that the angle of incidence on oil brine interface will be given as


now by Snell'a law at that interface we have

now we will have


now this is the angle of incidence for oil air interface
so now again by Snell's law we will have



Most probably physical, even though the change of liquids to solids is directly related to chemistry too
Answer:
the gravity required for stars and galaxies to orbit is much more than they produce, this leads us to believe there is invisible dark matter.