Q. If $\overrightarrow{\mathbf{a}}\ and\ \overrightarrow{\mathbf{b}}\$are unit vectors such that $\left\lbrack \overrightarrow{\mathbf{a}}\ \overrightarrow{\mathbf{b}}\ \overrightarrow{\mathbf{a}} \times \overrightarrow{\mathbf{b}} \right\rbrack = \frac{1}{4}$, then angle between $\overrightarrow{\mathbf{a}}\ and\ \overrightarrow{\mathbf{b}}$ is

A) $\frac{\pi}{3}$
B) $\frac{\pi}{4}$
C) $\frac{\pi}{6}$
D) $\frac{\pi}{2}$
Explanation

(c)
Given,
$\left( \overrightarrow{\mathbf{a}} \times \overrightarrow{\mathbf{b}} \right) \bullet \left( \overrightarrow{\mathbf{a}} \times \overrightarrow{\mathbf{b}} \right) = \frac{1}{4}$
$\Longrightarrow (\left| \overrightarrow{\mathbf{a}} \right|\left| \overrightarrow{\mathbf{b}} \right|\sin{\theta)}^{2} = \frac{1}{4}$
$\Longrightarrow \ \sin^{2}\theta = \frac{1}{4}$
$\Longrightarrow \ \theta = \frac{\pi}{6}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

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