A reflaction from (111) planes of a cubic crystal was observed ad at a glancing angle of ` 11.2^(@)` when X -rays of wavelength 154 pm were used. What is the length of the side of the unit cell ? `( sin 11.2^(@) = 0.1944)`

Explanation

To find the length of the side of the unit cell (A) for a cubic crystal given the reflection from (111) planes at a glancing angle of 11.2° and using X-rays of wavelength 154 pm, we will follow these steps:

### Step-by-Step Solution:

1. **Use Bragg's Law**:
Bragg's Law is given by the equation:
\[
n\lambda = 2D \sin \theta
...