# GENERAL GEOLOGY

## GEOLOGY

### CRYSTALLOGRAPHY

 Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
A certain type of crystal is having lattice constants in the ratio a:b:c is 0.424:1:0.367 . The Miller indicesof the plane whose intercepts are 0.212:1:0.183 is
 A (212) B (112) C (211) D (111)
Explanation:

Detailed explanation-1: -The orthorhombic crystal has axial units in the ratio of 0.424 : 1: 0.367. The miller indices of a crystal face whose intercepts are in the ratio 0.212 :1 :0.183 will be :-a)2 : 1 : 2b)1 : 2 : 1c)4 : 1 : 4d)2 : 1 : 1Correct answer is option ‘A’.

Detailed explanation-2: -By calculation, the miller indices of 2a, 3b, 4c is 6, 4, 3. Hence option 1 is correct.

Detailed explanation-3: -Miller indices (h, k, l) are expressed as a reciprocal of intercepts p, q, and r made by the plane on the three rectangular axes x, y, and z respectively. where, p = intercept of the plane on the x-axis, q = intercept of the plane on the y-axis, and r = intercept of the plane on the z-axis.

Detailed explanation-4: -The equation for a plane in three dimensions is exactly analogous for the line in two dimensions: x/a + y/b + z/c = 1. If line OP is perpendicular to the plane, its equation is also analogous to the two-dimensional case: xa = yb = zc.

Detailed explanation-5: -Hence, the miler indices are (122). Hence, the miller indices are (3¯¯¯¯22).

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