Of these electromagnetic waves, which has the A Over a unit distance, wave A has three crests and two troughs. The wave begins and ends at the rest position. B Over a unit distance, wave B has two crests and one trough. The wave begins at the rest position and ends at the top of a crest. C Over a unit distance, wave C has four crests and four troughs. The wave begins and ends at the rest position. longest wavelength?

Wave B has the longest wavelength

Explanation:

The wavelength of a wave is the distance between two consecutive points that are in phase.

The wavelength of a wave is also defined as the distance between successive crests or troughs along the z-axis.

A crest is the point of maximum upward displacement whereas a trough is a point of maximum downward displacement.

Comparing the three waves A, B and C over a unit distance.

Wave A:

Wave A has three crests and two troughs. The wave begins and ends at the rest position. There are 2½ successive points in phase in wave A

Therefore, the wavelength = 1/2.5 = 0.4

Wave B:

Over a unit distance, wave B has two crests and one trough. The wave begins at the rest position and ends at the top of a crest. There are 1¼ successive points in phase in wave B

Therefore, the wavelength = 1/1¼ = 0.8

Wave C:

Over a unit distance, wave C has four crests and four troughs. The wave begins and ends at the rest position.

There are 4 successive points in phase in wave B

Therefore, the wavelength = 1/4 = 0.25

Therefore, wave B has longest wavelength

the answer is a. at the equator