Please try again later. Ahmed Rashid, former Pakistani revolutionary, journalist and an expert on Taliban, explains why Pakistan is in a such a mess. He lists the factors that led Pakistan to the situation it is in right now.lease try again later. Ahmed Rashid, former Pakistani revolutionary, journalist and an expert on Taliban, explains why Pakistan is in a such a mess. He lists the factors that led Pakistan to the situation it is in right now.
Body waves travel through the interior of the Earth. On the other hand, surface waves propagate only at the interface between two different media, like the interface between Earth and atmosphere (i.e. the surface of the Earth).Body waves are of two types: Primary waves (also called P-waves, or pressure waves) and Secondary waves (S-waves, or shear waves).n the other hand, surface waves propagate only at the interface between two different media, like the interface between Earth and atmosphere (i.e. the surface of the Earth). Body waves are of two types: Primary waves (also called P-waves, or pressure waves) and Secondary waves (S-waves, or shear waves).
Definition of Mechanical Waves. A mechanical wave is a wave that is a vibration in matter, transferring energy through a material. Not all waves are like this. For example, electromagnetic waves such as visible light are not mechanical because they can travel through the vacuum of space to reach us from the sun. Mechanical waves include water waves, sound waves, earthquake waves, and many more. Like all waves, those of the mechanical variety have peaks, or crests, and troughs. They also have a frequency, which is the number of waves that pass by per second, and a wavelength, which is the distance from one peak to the next, or one trough to the next.