The energy of a photon is $3 \times 10^{-12} \ erg$. What is its wavelength in $nm$?
$(h = 6.62 \times 10^{-27} \ erg \cdot s; c = 3 \times 10^{10} \ cm/s)$

$A$ homogeneous equation of second degree in $x$ and $y$ represents which of the following?

If the force is given by $F = at + bt^2$,where $t$ is time,the dimensions of $a$ and $b$ are:

The vector sum of two forces is perpendicular to their vector difference. In that case,the forces

The angle between a pair of tangents drawn from a point $P$ to the circle $x^{2}+y^{2}+4x-6y+9 \sin^{2} \alpha + 13 \cos^{2} \alpha = 0$ is $2 \alpha$. The equation of the locus of the point $P$ is

For a cell,the terminal potential difference is $2.2 \, V$ when the circuit is open and reduces to $1.8 \, V$ when the cell is connected to an external resistance of $R = 5 \, \Omega$. Determine the internal resistance of the cell.