Find the range of frequency of light that is visible to an average human being (400 nm < λ < 700 nm).
We know that the velocity of light(c) is related with the frequency (
) and wavelength (
) of light as
Now, speed of light is 
Minimum wavelength , 
Associated frequency, 
Maximum wavelength , 
Associated frequency,
Hence the range of the frequency is 
to 
1