Three Flat Layers of Transparent Material Are Stacked Upon One

Multiple Choice

Three flat layers of transparent material are stacked upon one another.The top layer has index of refraction n₁,the middle has n₂ and the bottom one has n₃.If n₁ < n₂ < n₃,at what angle of incidence will a ray of light traverse the three layers in a single straight line?

A) θ_i ​= sin^-1(1/n​₁)
B) θ_i ​= sin^-1(1/(n​₁+n₂+n₃)
C) θ_i ​= tan^-1(1/(n​₁+n₂+n₃)
D) There is such an angle,but it is not given.