Question

Which of the following statements are true for the optically isotropic minerals?
A. They are opaque,
B. Light is transmitted with the same velocity in all directions through them,
C. Refractive index varies with direction of transmission of light,
D. Garnet is an optically isotropic mineral. Choose the correct answer from the options given below:

• A. A and B only
• B. A, B and C only
• C. B, C and D only
• D. B and D only

Hint:

Isotropic minerals have the same refractive index in all directions; garnet is an example.

Answer 1

The Correct Option is D

Concept:
Optically isotropic minerals have the same optical properties in all directions.

Step 1: Check statement A.
Optically isotropic minerals are not necessarily opaque. Many isotropic minerals transmit light. \[ A \text{ is incorrect} \]

Step 2: Check statement B.
In isotropic minerals, light travels with the same velocity in all directions. \[ B \text{ is correct} \]

Step 3: Check statement C.
If refractive index varies with direction, the mineral is anisotropic, not isotropic. \[ C \text{ is incorrect} \]

Step 4: Check statement D.
Garnet belongs to the cubic system and is optically isotropic. \[ D \text{ is correct} \] Thus, the correct statements are: \[ B,D \] \[ \therefore \text{Correct Answer is (D)} \]