The ratio of momentum thickness to displacement thickness for the boundary is given by which one of the following?

Question

The velocity profile in a laminar boundary layer is given by  $\frac{u}{U}=\frac{y}{\delta }$ . The ratio of momentum thickness to displacement thickness for the boundary is given by which one of the following?

                                           

a. 2 : 3                         b. 1 : 2

c. 1 : 6                         d. 1 : 3