Question

A sine function increasing through the origin can be used to model light waves. Violet light has a wavelength of 400 nanometers. Over which interval is the height of the wave decreasing, only?
(1) (0, 200)
(2) (100, 300)
(3) (200, 400)
(4) (300, 400)

Answer 1

Answer:

(2) (100, 300)

Step-by-step explanation:

One wave can be divided on 4 parts, as show on the picture.

Since a length of one whole wave equals 400, a length of each part is $400:4=100$ nanometers.

The height of the wave is decreasing on the second and on the third part, hence over the interval (100, 300).