Let $u$ and $v$ be two vectors. Then,$|u-v|=||u|-|v||$ if and only if

When a point source of monochromatic light is at a distance of $0.2\, m$ from a photoelectric cell,the cut-off voltage and the saturation current are $0.6\, V$ and $18\, mA$ respectively. If the same source is placed $0.6\, m$ away from the photoelectric cell,then:

Which one of the following is correct?

Which of the following is not used as a biopesticide?

The $pH$ of $0.1 \ M$ solution of the following salts increases in the order

The locus of the poles of focal chords of the parabola $y^2 = 4ax$ is