1.Every point on the wave executes an up down simple harmonic motion about the mean position. The point rises up, reaches the peak (crest) where it comes to rest momentarily, reverses direction and starts moving down reaching the lowest point (trough) where again is comes to rest before reversing direction. Thus, every point on the wave is in motion, either upward or downward except the points on the crests and troughs. The point on the peak (crest) is not blurred because it is stationary and those ahead and behind the peak are blurred because they are in motion (photograph of an object in motion is likely to be blurred).

2. Mechanical waves (which transfer mechanical energy) need a medium to propagate. For example sound waves need a medium such as air, water etc. Sound waves travel forward due to and fro vibrations of the molecules of the medium.

Electromagnetic waves (which transfer electromagnetic energy) do not need any medium to propagate. EM waves travel forward due to vibrations of the electric field and magnetic field vectors. Example : Light waves are EM waves.

3. In transverse waves, the vibrations of the medium molecules (in mechanical waves) take place perpendicular to the direction of propagation of the wave. Example : a stone dropped in a pond produces transverse waves as the water surface is seen to oscillate up and down whereas the wave propagates horizontally.

Attachment:- hw-4.zip