This paper utilizes the Reciprocal Law Two Times to prove that the rational number of a kind of form is not the integer, and proves that the number of another kind of prime is limitless.

X ray intensity was linearly related to the distance squared in the measured disance. The gradient was -2.04 confirming the validity of "disance inverse square law" in this experiment.

The design means of high frequency DCM flyback converter is derivated on the base of Faraday law of electromagnetic induction in subject.