Who is known as the father of Indian Bryology?

$A$ thin circular wire carrying a current $I$ has a magnetic moment $M$. The shape of the wire is changed to a square and it carries the same current. It will have a magnetic moment

$A$ capacitor of capacitance $C_0$ is charged to a potential $V_0$ and is connected with another capacitor of capacitance $C$ as shown. After closing the switch $S$,the common potential across the two capacitors becomes $V$. The capacitance $C$ is given by

Which one of the following statements is $WRONG$ in the context of $X-$rays generated from an $X-$ray tube?

$(x^2+y^2) dy = xy dx$. If $y(x_0) = e$ and $y(1) = 1$,then the value of $x_0$ is equal to

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