VITEEE 2015 Paper

Using prism formula,
µ =

sin( A+δm 2 )

sin( A 2 )

... (i)
where, A = angle of prism
δm angle of minimum deviation
Given, µ = cot(

A

2

) =

cos( A 2 )

sin( A 2 )

So, from Eq. (i)

cos( A 2 )

sin( A 2 )

=

sin( A+δm 2 )

sin( A 2 )

⇒ sin (

π

2

−

A

2

) = sin (

A

2

+

δm

2

)
⇒ δm = π - 2A = 180° - 2A