Answer:
24.2 degree
Step-by-step explanation:
n = 2.419
Let the minimum angle of incidence is i.
The value of minimum angle of incidence so that all the light reflects back into the diamond is the critical angle for air diamond interface.
The relation for the critical angle and the refractive index of diamond is given by
Sin ic = 1 / n
where, ic is the critical angle for air diamond interface and n be the refractive index for diamond.
Sin ic = 1 / 2.419 = 0.4133
ic = 24.4 degree
Thus, the value of minimum value of angle of incidence for which all the light reflects back into diamond is 24.4 degree.