The plot below shows the kinetic energy of ejected electrons as a function of the frequency of radiation done to study the photoelectric effect. Calculate the frequency at point A in s^-1 if it corresponds to light with a wavelength of 756 nm. 

At its farthest, the distance from Earth to the sun is 1.52 × 10¹⁰ km. If UV light from the sun has a frequency of 3.0 × 10¹⁶ Hz. Calculate the number of crests for the wave.

If an electromagnetic wave traveled for 54.6 ns, calculate the distance it traveled.

Heavy elements emit characteristics X-ray when their electrons undergo transitions. Shown below are the wavelengths of x-rays emitted by some elements:

Element          Wavelength (Å)
Cr                     2.291
Fe                     1.937
Co                    1.790
Cu                    1.542
Mo                    0.7107 

For each element, calculate the frequency (Hz) of the X-ray emitted.