Hi Friends! Consider an Ideal condition. suppose, I prepared a device which can generate and vary the frequency of a wave (you can consider the wave to be electromagnic wave). Using this device I studied following two scenarios: 1. I created a wave having frequency between 1014 to 1015 Hz. I passed this 1st waves thru vacuum, it passed easily. 2. Then I created a wave having frequency between 20 to 20,000 Hz Again I passed this 2nd wave thru vacuum, but it couldn't pass. You must be wondering, how can I be so sure, that wave will travel or not? Answer to this is: the first wave is the frequency of visible light wave(approx), and we all know light can travel thru vacuum. The frequency of second wave is that of human audible sound range, and it cannot travel thru vacuum. Why such behaviour, when both are same wave just different in frequency?