The light waves represented by the three rays shown in the diagram all have the same frequency. 4.7 wavelengths fit into layer 1, 3.2 wavelengths fit into layer 2, and 5.3 wavelengths fit into layer 3. Rank the layers according to the speeds of the waves, least to greatest.
A) 1, 2, 3
B) 2, 1, 3
C) 3, 1, 2
D) 3, 2, 1
E) 1, 3, 2

Question

The light waves represented by the three rays shown in the diagram all have the same frequency. 4.7 wavelengths fit into layer 1, 3.2 wavelengths fit into layer 2, and 5.3 wavelengths fit into layer 3. Rank the layers according to the speeds of the waves, least to greatest. 
A) 1, 2, 3 
B) 2, 1, 3 
C) 3, 1, 2 
D) 3, 2, 1 
E) 1, 3, 2

Quizplus · Accepted Answer

The speed of a wave is directly proportional to the wavelength, so the layer with the longest wavelength (layer 3) has the fastest wave speed, followed by layer 2 and then layer 1. Therefore, the correct ranking from least to greatest speed is 3, 2, 1. The answer is D.

The Light Waves Represented by the Three Rays Shown in the Diagram