Week 3 Lecture 5
Solutions at the bottom.

1)  In-video quiz at timepoint 00:28.

The electromagnetic force is one of the four fundamental interactions in nature, the other three being the strong interaction, the weak interaction, and gravitation. This force is described by electromagnetic fields, and has innumerable physical instances including the interaction of electrically charged particles and the interaction of uncharged magnetic force fields with electrical conductors.

Wikipedia - Electromagnetism, http://en.wikipedia.org/wiki/Electromagnetism

2)  In-video quiz at timepoint 08:20.

"In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats."

Wikipedia - wavelength, http://en.wikipedia.org/wiki/Wavelength