A hypothetical equation is given as $\rho = a \sqrt{P} + bT^2$, where $\rho$ is density, $P$ is pressure, and $T$ is temperature. The dimensions of $\frac{a}{b}$ are:

Wavelength of ray of light is 0.00006 m. It is equal to

How many wavelengths of $K{r^{86}}{\rm{\;}}$ are there in one metre