Question

which unit is most convenient for expressing the dimensions of a polio virus, which is about 2.8×10⁻⁸ m in diameter?
μm
mm
nm
mm

Explanation:

Step1: Recall unit - conversion factors

1 $\mu m=10^{- 6}m$, 1 $mm = 10^{-3}m$, 1 $nm=10^{-9}m$, 1 $Mm = 10^{6}m$.

Step2: Convert the diameter of the polio - virus to different units

Convert $2.8\times10^{-8}m$ to $\mu m$: $\frac{2.8\times10^{-8}m}{10^{-6}m/\mu m}=2.8\times10^{-2}\mu m$.
Convert $2.8\times10^{-8}m$ to $mm$: $\frac{2.8\times10^{-8}m}{10^{-3}m/mm}=2.8\times10^{-5}mm$.
Convert $2.8\times10^{-8}m$ to $nm$: $\frac{2.8\times10^{-8}m}{10^{-9}m/nm}=28nm$.
Convert $2.8\times10^{-8}m$ to $Mm$: $\frac{2.8\times10^{-8}m}{10^{6}m/Mm}=2.8\times10^{-14}Mm$.

Step3: Determine the most convenient unit

The value $28nm$ is a non - scientific notation value that is easy to read and work with compared to the other converted values.

Answer:

C. nm