Answer:
(a) has the highest frequency
Explanation:
E = hf...where E(is the energy of a photon);h(is the planck's constant) and f is the frequency of the photon
Whereby this formula shows us that energy of a photon is directly proportional to its frequency
So hence if the energy is high then the frequency of the photon is also high
Echo means repetition of sound..If someone is speaking there will be two sounds..one which he is speaking right now and the other sound which he/she spoke earlier ..this will lead to confusion..in big halls the distance would be more than 17 m between the walls which will cause echo and not reverberation(prolongation of sound)
Hope this helps!
Static friction is the friction between an object at rest and the surface on which it is resting on.
Kinetic friction is the friction between a moving object and the surface on which it moves.
Hopefully you understood and this helps :)