posted by mary .
What is the frequency of a photon with an energy of 7.40 10-18 J? (The speed of light in a vacuum is 2.998 108 m/s. Planck's constant is 6.626 10-34 J·s.)
You may have got this question in a chem glass, but it is really about physics.
E = h*frequency is the equation to use
h is Planck's constant, which you were given.
Solve for the frequency, in s^-1 (also called Hz)
You don't need to use the speed of light to answer this question. You would need that for the wavelength.