A ray of light incident on an equilateral prism ( refractive index=√3) moves parallel to base of prism inside it. What is the angle of incidence for this ray ?

Since light incident on the prism is parallel to base of prism , it is case of minimum deviation

so , 2r=A , r=A/2=30° ...(where r=angle of refraction & A=angle of prism)

now , using snell's law , sini/sinr = mu2/mu1

sini=root3 × 1/2

i=60°