Cracking the SAT Physics Subject Test

Although we’re dealing

with two mediums

now, remember that Rule

#1 still applies while

the wave is in the first

medium (speed does not

change) and will apply

again once it enters the

second medium.

When that happens, the

wave takes on a direct

relationship between its

wave speed v and

wavelength λ:

v 1 /λ 1 = v 2 /λ 2

5. Two ropes of unequal linear densities are connected, and a
   wave is created in the rope on the left, which propagates to the right,
   toward the interface with the heavier rope.

When a wave strikes the boundary to a new medium (in this

case, the heavier rope), some of the wave’s energy is reflected

and some is transmitted. How do the speed and wavelength of

the incident wave compare with the speed and wavelength of

the transmitted wave?

Here’s How to Crack It

Since the wave enters a new medium, it will have a new wave speed. Because rope