If the pair of straight lines given by $A x^2+2 H x y+B y^2=0$,where $(H^2 > A B)$,forms an equilateral triangle with the line $a x+b y+c=0$,then $(A+3 B)(3 A+B)=$ (in $H^2$)

The potential difference between $A$ and $B$ in the figure is .............. $V$.

The following figure shows the multiple reflections of a light ray along a glass corridor where the walls are either parallel or perpendicular to one another. If the angle of incidence at point $P$ is $30^o$,what are the angles of reflection of the light ray at points $Q, R, S$,and $T$ respectively?

$A$ magnet freely suspended in a vibration magnetometer makes $40$ oscillations per minute at place $A$ and $20$ oscillations per minute at a place $B$. If the horizontal component of earth's magnetic field at $A$ is $36 \times 10^{-6} ~T$,then its value at $B$ is

What is the size of $Wolffia$ $globosa$?

The mass defect for the nucleus of helium is $0.0303 \, a.m.u.$ What is the binding energy per nucleon for helium in $MeV$?