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# Two glass prisms of refractive index $1.5$ and $1.6$ are kept in contact and a ray of light is incident on this combination of prism. The light emerges out of this combination un deviation The angle of prism of refractive index $1.6$ is $5^{\circ}$ What is angle of prism of the other prism.

$(a)\;6^{\circ} \\ (b)\;5^{\circ} \\ (c)\;4^{\circ} \\ (d)\;3^{\circ}$

Since the ray undergoes no deviation the deviation produced by 1st must be equal to deviation produced by the 2nd $\delta_1 =\delta_2$
$(\mu_1-1)A_1= (\mu_2-1)A_2$
$(1.5-1 )A_1 =(1.6 -1)5^{\circ}$
$A_1= 6^{\circ}$
Hence a is the correct answer.