Dr Gulshan S. answered • 04/24/21

PhD In Physics and experience of teaching IB Physics and Math High sc

This happens only at angel of minimum deviation, which is different for different colors.

For angle of minimum deviation setting ( Angle of incidence = angle of emergence, deviation angle is minimum)

µ = Sin (A+D/2) / Sin A/2

Where A = Angle of prism ( Generally 60^{0 })

and D = Angle of Minimum Deviation for particular color, For Example if A= 60^{0 }, D = 45 ^{0 }9 For blue light )

µ ( for particular color of light ) = Sin ( 60 + 45)/2 / Sin A/2 = Sin 105/2 / Sin 60/2= Sin 52.5 / Sin 30

= 2*0.7933 = 1.586 ( for blue light )

For Red color of light D will be smaller than 45 ( Say 40 ^{0 })

µ ( For Red light ) = Sin 50/sin 30 = 1.53

Airah M.

Oh i get it sir. what about the reason that at some angle of incidence, the incident ray will not be refracted by the prism and will just pass through the prism in a straight line? Like the angle of incidence is not basically set to zero but still no refaction of light happens how is this so?04/24/21