The radius of a proton is about `10^(-9)` micron and the radius of universe is about `10^(28)` cm. Name a physical object whose size is approximately halfl way between these two extermes on a logarithmin scale.

Explanation

Here, radius of proton,
`r_1 = 10^(-9) micron =10^(-15)m`
and radius of universe,
`r -2 = 10^(28) cm = 10^(26)m`
If r is the size half way between these two on a logarithimc scale, then
`log r = (log r_1 + log r_2)/(2) = (log 10^(-15) + log 10^(26))/(2)`
`=(-15 + 26)/(2) =5.5 ~= 6`
` :. r =10^6 metre`
This is the order of radius of earth. Hence the physical object is earth.