A.15×10-4rad B.10×10-4rad C.7.5×10-4rad D.5×10-4rad
A.sin-1(0.37968) B.sin-1(0.75936) C.sin-1(0.18964) D.cos-1(0.37968)
A.(α+b)λ/2αa B.bλ/2αa C.(α+b)λ/2α D.(a+b)λ