The scientific name of the earthworm is ....

An electron in a Hydrogen atom first jumps from the third excited state to the second excited state and then from the second excited state to the first excited state. The ratio of the wavelengths $\lambda_{1} : \lambda_{2}$ emitted in the two cases respectively is:

The equation of the line passing through the point of intersection of the lines $x-3y+2=0$ and $2x+5y-7=0$ and perpendicular to the line $3x+2y+5=0$ is:

Five identical springs are used in the following three configurations. The time periods of vertical oscillations in configurations $(i)$,$(ii)$ and $(iii)$ are in the ratio:

Which of the following is a secondary pollutant?

In Young's double slit experiment,the seventh maximum with wavelength ${\lambda _1}$ is at a distance $d_1$ from the central maxima,and the same maximum with wavelength ${\lambda _2}$ is at a distance $d_2$. Then the ratio $d_1/d_2$ is: