The frequency of the infrared wave with wavelength of 4 × 10^-6 meters is 7.495 × 10^13 Hz. The relationship between frequency (f) of the wave, its wavelength (λ), and the speed of light (c) is given in the formula: f = c/λ. We know that c = 2.998 × 10^8 m/s and that λ = 4 × 10^-6 m. From here, f = 2.998 × 10^8 m/s / 4 × 10^-6 m = 2.998/4 × 10^(8-(-6)) 1/s = 0.7495 × 10^14 Hz = 7.495 × 10^-1 × 10^14 Hz = 7.495 × 10^(-1+14) Hz = 7.495 × 10^13 Hz
