Which statement best describes the relationship between wavelength and speed in fiber optics?

Which statement best describes the relationship between wavelength and speed in fiber optics?

• A. Some wavelengths travel faster than others
• B. All wavelengths travel at the same speed
• C. Wavelength determines color but not speed
• D. Speed is independent of wavelength and medium

Answer: (A)

Light in a fiber travels at a speed determined by the medium’s refractive index, which changes with wavelength. Since v = c / n(λ), different wavelengths see different indices and therefore move at different speeds. That varying speed with wavelength is dispersion, so some wavelengths travel faster than others. The other statements ignore this wavelength‑dependent speed or claim speed is unrelated to wavelength, which isn’t true in real fibers.

Light in a fiber travels at a speed determined by the medium’s refractive index, which changes with wavelength. Since v = c / n(λ), different wavelengths see different indices and therefore move at different speeds. That varying speed with wavelength is dispersion, so some wavelengths travel faster than others. The other statements ignore this wavelength‑dependent speed or claim speed is unrelated to wavelength, which isn’t true in real fibers.