Question

The speed of an electromagnetic wave is a constant, 3.0 × 108 m/s. The wavelength of a wave is 0.3 meters. What is the frequency? A. 9.0 × 108 Hz B. 1.0 × 109 Hz C. 1.0 × 108 Hz D. 9.0 × 107 Hz

Answer 1

Answer: option B. 1.0 × 10⁹ Hz

Explanation:

The speed, s, of a wave, equals the product of its frequency, ν, times its wavelength, λ:

• s = νλ.

As the question states, the speed of an electromagnetic wave is a constant, c, equal to 3.0 × 10⁸ m/s.

Substituting this constant in the equation for the speed of the wave, you get:

• c =  νλ.

From that equation, you can solve for the frequency to show the inverse realation of frequency and wavelength:

• ν =  c / λ

Now, you just have to substitute values and compute:

• ν =  c / λ = 3.0 × 10⁸ m/s / 0.3m = 10. × 10⁸ Hz = 1.0 × 10⁹ Hz