Propagation of Waves & Pulses
- As a pulse passes through a medium, for example a coiled spring, the motion of any given point along the spring is in the same direction as that of the pulse.As the pulse moves through the spring its amplitude decreases.
- The speed of the pulse remains constant throughout the length of the medium.
- The speed of the pulse does not depended on the amplitude of the pulses.
- As the tension of the spring increases, the speed of the pulse also increases.
When the pulse is reflected at the other end of the spring, it reverses in direction. Positive pulses become negative and vice versa.
Reflection of Waves and Pulses
- Transmitted and reflected waves move along the same line of action in a medium but in opposite directions.
- When “positive” water waves hit a straight barrier, they reflect along the same path but as negative waves.
- The speed of the reflected waves is the same as the speed of the transmitted waves
- The wavelength of the reflected waves is the same as the wavelength of the transmitted waves
- Near the barrier destructive interference can be seen as negative pulses meet positive pulses.
At these points the water seems to be standing still (standing waves are formed here).
- When an incident wave front hits a barrier at an angle other than 900, the reflected waves will bounce back at the same angle to the normal with the barrier. The angle of incidence is equal to the angle of reflection. (Law of Reflection of waves)
- When straight waves hit a semi-circular barrier they are reflected as circular waves and come together (converge) in one point called the focal point.
Refraction of Waves
- If we observe waves traveling from deep water to shallow water in a straight line, we note that while the direction on transmission of the waves does not change both the speed and the wavelength of the wave’s decreases. The opposite occurs when they travel from shallow to deep waters.
- When waves travel at an angle from deep water to shallow water the direction of motion also changes.
- When waves slow down they bend away from the normal
In general, deep waters are a fast medium for wave travel whereas shallow waters are a slow medium.Mechanical Resonance
All object have a "natural frequency" that defines their molecular or atomic structure.
If an object is subjected to vibrations from a nearby source that correspond to its natural frequency it will start to oscillate (vibrate) at that frequency