Question

The crystal system with edge lengths \( a \ne b \ne c \) and axial angles \( \alpha = \beta = \gamma = 90^\circ \) is 'x' and number of Bravais lattices for it is 'y'. x and y are

• A. Cubic ; 3
• B. Monoclinic ; 2
• C. Orthorhombic ; 4
• D. Trigonal ; 2

Hint:

Orthorhombic system: \( a \ne b \ne c \) and \( \alpha = \beta = \gamma = 90^\circ \). It has the second-highest number of Bravais lattices (4), after the cubic system (3).

Answer 1

The Correct Option is C

Step 1: Identify the crystal system

Given:

• Edge lengths: \( a \ne b \ne c \)
• Angles: \( \alpha = \beta = \gamma = 90^\circ \)

This matches the Orthorhombic crystal system, where all edges are unequal but all angles are 90°.

Step 2: Count the number of Bravais lattices

The orthorhombic system has 4 types of Bravais lattices:

• Simple (P)
• Body-centered (I)
• Base-centered (C)
• Face-centered (F)