Question

Calculate the wavelength, frequency and wavenumber of a light wave whose period is 2.0 * $10^{-10}$ s.

NCERT Class XII
Chemistry - Main Course Book I

Chapter 2. Structure of Atom

Answer 1

Time period T = 2.0 * 10⁻¹⁰ seconds  = 0.2 nano seconds
wave length = λ = c / f

frequency =  f = 1/T = 5 * 10⁹ Hz  = 5 GHz

   wave length = 2.98 * 10⁸ m/sec  / 5 * 10⁹ Hz
               λ  = 0.0596 meters

  we know that:         k λ = ω T = 2 π f T  = 2 π

   k = ω / c  or,
   wave number = k = 2 π / λ =  105.44 radians per meter