The magnifying power of a refracting type of astronomical telescope is $m$. If the focal length of the eyepiece is doubled,the magnifying power will become:

$A$ magnetic needle lying parallel to a magnetic field is turned through $60^{\circ}$. The work done on it is $W$. The torque required to maintain the magnetic needle in the position mentioned above is

Haemozoin is a

If the amplitude of $z - 2 - 3i$ is $\pi / 4$,then the locus of $z = x + iy$ is

If you suspect a major deficiency of antibodies in a person,to which of the following would you look for confirmatory evidence?

$A$ body of mass $m = 10^{-2} \; kg$ is moving in a medium and experiences a frictional force $F = -kv^2$. Its initial speed is $v_0 = 10 \; m/s$. If,after $10 \; s$,its energy is $\frac{1}{8} mv_0^2$,the value of $k$ will be: