How long would it take a radio wave of frequency `6xx10^(3) sec^(-1)` to travel from mars to the earth, a distance of `8xx10^(7)km` ?

Explanation

Distance to be travelled from mars to earth
`=8xx10^(7)km`
`=8xx10^(10)m`
`because` Velocity of `EM` waves `=3xx10^(8)m//sec`
`therefore` Time `=("Distance")/("Velocity")`
`=(8xx10^(10)m)/(3xx10^(8)m//sec^(-1)) = 2.66 xx10^(2)sec`.
Note : Cosmic rays are made of high velocity sub-atomic particle like protons, neutrons etc which enter earth's atmosphere from outer space. They are not `EM` wave.