Enter the force constant (N/cm) and the reduced mass (kg) into the Absorption Frequency Calculator. The calculator will evaluate the Absorption Frequency. 

Absorption Frequency Formula

The following two example problems outline the steps and information needed to calculate the Absorption Frequency.

AF = 1/2*pi * (k/u)^{(1/2)}


  • AF is the Absorption Frequency (1/cm)
  • k is the force constant (N/cm) 
  • u is the reduced mass (kg) 

To calculate the absorption frequency, multiply pi by the ratio of the force constant divided by the reduced mass raised to the one-half power, then divide the result by 2.

How to Calculate Absorption Frequency?

The following steps outline how to calculate the Absorption Frequency.

  1. First, determine the force constant (N/cm). 
  2. Next, determine the reduced mass (kg). 
  3. Next, gather the formula from above = AF = 1/2*pi * (k/u)^(1/2).
  4. Finally, calculate the Absorption Frequency.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

force constant (N/cm) = 30

reduced mass (kg) = 5

AF = 1/2*pi * (k/u)^(1/2) = ?