GATE 2021 MT – Question 31
An FCC crystal’s first X-ray reflection is at Bragg angle $\theta=30^\circ$. The second reflection has Bragg angle ______ degrees (one decimal place).
Practise this question in The GATE Grind →
Show answer and explanation
Correct answer: 34.8 to 36.1
Explanation
The first two allowed reflections are 111 and 200. At fixed wavelength, sinθ2/sinθ1=√(4/3). With θ1=30°, sinθ2=1/√3, giving **θ2=35.3°**.