What is the range of frequencies of visible light?

Question

The wavelengths of visible light range from 400nm to 700nm, and 1nm is 10^-9.

Answer 1

v = λf

f = v/λ

v, the velocity, is the speed of light, which is equal to 3.00 * 10^8 m/s.

λ = 400nm = 4 * 10^-7 m

f = (3 * 10^8) / (4 * 10^-7) = 7.5 * 10^14 Hz

λ = 700nm = 7 * 10^-7m

f = (3 * 10^8) / (7 * 10^-7) ~= 4.3 * 10^14 Hz

Range = 4.3 * 10^14 Hz - 7.5 * 10^14 Hz

Answer 2

λf = c = 3*10⁸m/s (speed of light)

f = 3*10⁸m/s / 400 nm

f = 3*10⁸m/s / 400e-9m

f = 3*10⁸m/s / 4e-7m

f = 0.75 e15 Hz

f = 3*10⁸m/s / 700e-9m

f = 0.43 e15 Hz