Determine the frequency of light with a wavelength of 3.835 × 10−7 cm. answer in units of hz.

 First convert the wavelength to meters: 
λ = 3.835 × 10^−7 cm is 0.003835 in meters

The speed of light is: 
C = 3.0 × 10^8 m/s 
Frequency is the speed the wavelength: 
f = C/λ where c is speed of light and λ is the length of the wave
f = 3 × 10^8 m/s/ 0.003835 m 
f = 7.8227 × 10^10 Hz