Refraction
Definition
Requires:
Refraction is transmission with a bend. Refraction is a change
in direction as sound transmits from one medium to
another.
Occurs when two conditions are met ψ:
1. oblique incidence and
2. different propagation speeds ψ.
Each and every angle has a
Cannot occur with normal incidence or with identical
propagation speeds.
page 2 for a chart of typical
angles and their respective
sines.
Snell’s Law
Sine
sine associated with it. See
The physics of refraction are described by Snell's Law. ψ
Equation
sine (transmission angle)
propagation speed 2
---------------------------------------------------------------------------- = ------------------------------------------------------------sine (incident angle)
propagation speed 1
Examples
If propagation speed 2 is less than propagation speed 1, then
the transmission angle is less than the incident angle. ψ
If propagation speed 2 is greater than propagation speed 1,
the transmission angle is greater than the incident angle.ψ
Medium 2 Slower
1
>
Same Speeds
2
1
I
=
Medium 2 Faster
2
1
I
<
2
I
T1
T2
T3
no refraction with
same speeds
48 · Interaction of Sound and Media
ESP, Inc.©2006