Davisson-Calbick formula

Davisson-Calbick formula

[¦da·və·sən ′kal·bik ‚fȯr·myə·lə]
(electronics)
A formula which states that the focal length of a simple electrostatic lens consisting of a circular hole in a conducting plate is equal to four times the potential of the plate divided by the difference in the potential gradients on either side of the plate.