In the wavelength calculation for meters, which speed is used in the numerator?

In the wavelength calculation for meters, which speed is used in the numerator?

• A. 300,000,000
• B. 299,792,458
• C. 3,000,000
• D. 30,000,000

Answer: (A)

Wavelength is found from the relation λ = v / f, where v is how fast the wave travels. For electromagnetic waves in free space, that speed is the speed of light, c. So in meters and hertz, the wavelength is λ = c / f. The exact value of c is 299,792,458 m/s, but for simple calculations we commonly use the rounded value 3.00×10^8 m/s, i.e., 300,000,000 m/s. That’s why the speed in the numerator is taken as 300,000,000—to get a quick, reasonably accurate wavelength. If higher precision is needed, use 299,792,458 m/s.

Wavelength is found from the relation λ = v / f, where v is how fast the wave travels. For electromagnetic waves in free space, that speed is the speed of light, c. So in meters and hertz, the wavelength is λ = c / f. The exact value of c is 299,792,458 m/s, but for simple calculations we commonly use the rounded value 3.00×10^8 m/s, i.e., 300,000,000 m/s. That’s why the speed in the numerator is taken as 300,000,000—to get a quick, reasonably accurate wavelength. If higher precision is needed, use 299,792,458 m/s.