it is observed that in outer space sound cannot be here why is it so can describe an activity to support your claim
Answers
I'm afraid that your friends are right. In empty space, there is no air, and what we call "sound" is actually vibrations in the air. Now, like you've said, there are indeed light waves and radio waves in space, but these waves are not sound, but light. Light does not need air to travel, but then you don't hear it; you see it, or it is interpreted by your radio set and then translated into sound.
Astronauts in space do talk to each other. In the spacecraft, there is plenty of air, so they just talk normally. When they are spacewalking, they talk by means of radios in their helmets. The radio waves, again, have no problem in space, but they're not sound. They're radio, which has to be converted into sound by the astronauts' headsets.
In outer space, we can't hear the sound.
This is because space is a vaccum. Sound doesn't travel through vaccum as it need a medium to travel.