When a ray of light enters a medium of refractive index μ, it is observed that the angle of refraction is half of the angle of incidence, then angle of incidence is
A. 2cos⁻¹(μ)
B. 2cos⁻¹(μ/2)
C. 2cos⁻¹(μ)
D. 2sin⁻¹(μ/2)