Fluid clutches are used on equipment that is subjected to higher torque per unit volume. This type of clutch makes use of an incompressible fluid like oil in order to transfer the input of a movement from a pedal and cylinder to an actuating cylinder. Releasing the this clutch would stop the transfer of power but still allowing the engine to turn continuously.
Answer:

Explanation:
Let the speed of light in vacuum is c and the speed of light in medium is v. Let the angle of incidence is i.
By using the definition of refractive index
refractive index of the medium is given by
n = speed of light in vacuum / speed of light in medium
n = c / v ..... (1)
Use Snell's law
n = Sin i / Sin r
Where, r be the angle of refraction
From equation (1)
c / v = Sin i / Sin r
Sin r = v Sin i / c
