The prefix $10^{18}$ is

Explain the scientific notation method of measurement.

Round the number $234555359$ to $3$ significant figures.

The candela is the luminous intensity,in a given direction,of a source that emits monochromatic radiation of frequency '$A$' $\times 10^{12}$ hertz and that has a radiant intensity in that direction of $\frac{1}{B}$ watt per steradian. '$A$' and '$B$' are respectively

If the speed of light is $3.0 \times 10^8 \ ms^{-1}$,calculate the distance covered by light in $2.00 \ ns$. (in $m$)

One fermi is $....$ (in $cm$).