# Newton's formula

## Newton's formula

An expression relating the focal lengths of an optical system (f and f′) and the object x and image x′ distances measured from the respective focal points. Thus,
ff′ = xx
If the optical system is a lens in air −f = f′ and the formula becomes
f2 = xx
Syn. Newton's equation; Newton's relation. See fundamental paraxial equation; sign convention; gaussian theory.
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References in periodicals archive ?
The images gave a value of 0.86 for the deflection, about in line with Newton's formula, but with large uncertainties.
Hu Ning according to general relativity and Binet's formula, we get the following improved Newton's formula of universal gravitation
 Fu Yuhua, Improved Newton's formula of universal gravitation, Ziranzazhi (Nature Journal), 2001(1), 58-59
3 With the help of general relativity and accurate experimental data to derive the improved Newton's formula of universal gravitation
Hu Ning derived an equation according to general relativity, with the help of Hu's equation and Binet's formula, we get the following improved Newton's formula of universal gravitation
So, by substituting [R.sub.0][c.sup.2]/[M.sub.0] for G in Newton's formula, the gravitational potential energy Ug stored in a system of masses M and m separated by a distance r can be expressed as:
By applying Newton's formula, a planet's future path can be told from its present position and velocity and all the gravitational pulls that it experiences.
There are the two following analogues of Newton's formula (3.1):
YOU CAN CALCULATE recoil kinetic energy with Sir Isaac Newton's formula: KE = M[V.sup.2]/ GC, where M is a rifle's mass and V is velocity.