An ultraviolet wave traveling through a vacuum has a wavelength of 4.0 * 10-7 m. The wave's frequency, written in scientific notation to two significant figures, is * 1014 Hz.

We can use the equation c=hn to calculate the frequency, where ‘c’ is the speed of light in a vacuum (2.998x10^8 m/s), ‘h’ is the wavelength, and ‘n’ is the frequency.

Plug the values you have into the equation and solve.

c=hn

(2.998x10^8) = (4x10^-7) n

n=7.495x10^14

The frequency of this wave is 7.495x10^14 Hz.

round the answer to 7.5 x10^14