# For the angle of minimum deviation of a prism to be equal to its refracting angle, the prism must be made of a material whose refractive index: Option 1) lies between 2 and  Option 2) is less than 1 Option 3) is greater than 2 Option 4) lies between and 1

$\mu\:=\:\frac{Sin (\frac{A+\delta m}{2})}{Sin(\frac{A}{2})}.0$

Here $\delta _{m}\:=\:A\:\:\:\:\:\:\:\:\therefore\mu\:=\:\frac{Sin(\frac{A+A}{2})}{Sin(\frac{A}{2})}$

$\mu-2Cos\frac{A}{2}------1$

In the given situation A can varies from 0 to 90.

$\therefore\:\mu_{mim}-2.Cos(\frac{90}{2})-\sqrt{2}$

$\mu_{max}-2.Cos0^{\circ}=2$

$\therefore\:\mu$ lies between $\sqrt{2}$ and 2.

Option 1)

lies between 2 and

This option is correct.

Option 2)

is less than 1

This option is incorrect.

Option 3)

is greater than 2

This option is incorrect.

Option 4)

lies between and 1

This option is incorrect.

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