Contd...

Since is quite small, , and

(17)

Let be the final angle of refraction with which the laser beam emerges into the surrounding air. For the optical window-air combination,

(18)

Substituting the value of from Equation 17 into Equation 18, the angle with which the laser beam emerges into the surrounding medium can be expressed as

(19)

or

(20)

Since

(21)

Hence a correction factor equal to the refractive index of the KDP solution at the ambient temperature is taken into consideration for calculating the angle at which the laser beam emerges into the surrounding medium.