(b) Here, $y_{1} = \frac{1}{2}\sin{\omega t + \frac{\sqrt{3}}{2}\cos{\omega t}}$
= $\cos{\frac{\pi}{3}\sin{\omega t + \sin{\frac{\pi}{2}\cos{\omega t}}}}$
$\therefore$ $y_{1} = \sin\left( \omega t + \frac{\pi}{3} \right)$
Similarly, $y_{2} = \sqrt{2}\sin\left( \omega t + \frac{\pi}{4} \right)$
$\therefore$ Phase difference $\mathrm{\Delta}\varnothing = \frac{\pi}{3} - \frac{\pi}{4} = \frac{\pi}{12}$