2.3 General Behavior of Waves

1. Reflection2. Refraction3. Interference4. Diffraction

Reflection

The law of reflection:

The angle of incidence = The angle of reflection.

ri

Reflection and Huygens’s wavelets

Parabolic Reflector

Ellipse

Whispering Chamber

Refraction

The bending of a wave as it passes from one medium to another is called refraction.

Refraction is due to changes in Wavespeed

Refraction and Speed of the Wave

Refraction of wavesIllustrated using Huygens’s

wavelets

Waves at a beach

Voices travel further at night, than during the day

With the wind or Into the wind

Range of thunder

Interference

Interference refers to the combining or addition of two similar waves.

Interference can be destructive, resulting in the effective disappearance of the waves, when they are out of phase.

It can be constructive, resulting in the enhancement of the waves, when they are in phase.

Destructive Interference

Constructive Interference

Quincke’s Interference Tube

Path Length Difference and Interference

Interference along antinodal and nodal lines

Noise-canceling headphones utilize destructive interference

Diffraction of Sound

Diffraction Diffraction is the bending of waves around obstacles or the edges of an opening in the same medium.

It can be explained using Huygens’s principle.

The amount of diffraction depends on the nature of waves and their wavelength.

Sound waves diffract much more than light waves.

Low-frequency (high-wavelength) sound waves diffract more than high-frequency (low-wavelength) light waves.

Diffraction in Speakers

Small-diameter speakers, called tweeters, are used to produce high-frequency sound. The small diameter helps to promote a wider dispersion of the sound.

The amount of bending is depends on the ratio: λ/w, λ is the wavelength and w is the width of the opening.