When a glass prism of refracting angle $60^{\circ}$ is immersed in a liquid,its angle of minimum deviation is $30^{\circ}$. The critical angle of glass with respect to the liquid medium is (in $^{\circ}$)

If $f: R \rightarrow R$ is defined by $f(x) = \begin{cases} \frac{2 \sin x - \sin 2x}{2x \cos x}, & \text{if } x \neq 0 \\ a, & \text{if } x = 0 \end{cases}$,then the value of $a$ so that $f$ is continuous at $x = 0$ is

Sulphur on boiling with $NaOH$ solution gives

Complete hydrolysis of cellulose yields ........

If $a$ and $b$ are unit vectors such that $(a + 2b)$ and $(5a - 4b)$ are perpendicular to each other,then the angle between $a$ and $b$ is ................... $^o$.

Two ions having masses in the ratio $1:1$ and charges in the ratio $1:2$ are projected into a uniform magnetic field perpendicular to the field with speeds in the ratio $2:3$. The ratio of the radii of the circular paths along which the two particles move is