Waves and Wave Motion

M1.14 + M1.15

How are mechanical waves generated?

When energy is mechanically imparted to disturb a continuous material medium, particles that are directly receiving this energy are forced to vibrate.

Where are the crests, troughs, wavelength and amplitude?

What is a time period on a wave?

time between two successive crests/troughs

What is the difference between transverse and longitudinal wave?

transverse waves occur when particles vibrate in a direction perpendicular to wave propagation

When is wave inverted upon reflection?

When medium B is denser than medium A

What is this phenomenon called?

refraction

Water waves in a ripple tank is described by the equation*

y = 0.050 sin [2π(25t – 2x)]

where x and y are in m and t in s. Determine

a) the frequency

b) the wavelength and

c) the speed of the waves

a) 25 Hz, b) 0.5 m c) 12.5 m/s

Define diffraction.

the bending of waves around the edge of an object or through a small aperture.

What causes more diffraction?

when the aperture (the sides on the ends) is smaller as the wavelength, giving the maximum amount of diffraction

What are the Principle of Superposition?

“At any time, the combined waveform of two or more interfering waves  is given by the sum of the displacements of the individual waves at each point in the medium.”

What is constructive interference?

in constructive interference, displacements of pulse waves are in the same direction, which causes the amplitude of the combined waveform to be larger than the pulse waves

What is destructive interference?

in destructive interference, the pulse waves tend to cancel each other when they meet, and the amplitude of the combined waveform is smaller than the pulse waves

What is the Doppler’s effect?

the change in frequency or wavelength of a wave as perceived by an observer moving relative to the wave's source

When the observer is behind the source of the sound, what happens to the pitch and wavelength

lower pitch, longer wavelength

A student reading his Physics book on a lake dock notices that the distance between two incoming wave crests is about 2.4 m, and he then measures the time of arrival between wave crests to be 1.6 s. What is the approximate speed of the waves?

1.5m/s