Combined Lens Power Calculator
Adds the powers of ideal thin lenses in contact. Changing an input recalculates the output without hiding the substitution.
Supply the lens or mirror data
Combined power
The geometry behind the output
Adds the powers of ideal thin lenses in contact. The calculation keeps first lens power, second lens power visible and reports combined power in D.
A finite air gap between lenses introduces an additional separation term and cannot be modeled by simple addition.
The combined lens power page labels each value before it enters the equation. That prevents an angle convention, temperature scale, optical sign, or reference quantity from becoming an invisible assumption.
Following Ptotal = P₁ + P₂
For combined lens power, identify combined power as the sought quantity and copy the printed relationship before using the sample data. This establishes an auditable direction for the arithmetic.
Keep the sign convention and denominator explicit in Ptotal = P₁ + P₂; a finite answer alone does not prove that the setup is physical.
Check the image sign and magnitude
Reduce the dimensions in Ptotal = P₁ + P₂ until they agree with D. For logarithms, trigonometric functions, and ratios, also verify that their arguments are dimensionless and inside the permitted domain.
Change one source value slightly and predict the direction of combined power first. If the screen moves the other way, revisit the equation, signs, and reference frame.
Where Combined Lens Power stops being sufficient
The combined lens power relationship uses paraxial rays or an ideal interference geometry. Thick elements, aberrations, polarization, dispersion, and large angles may require a more complete optical model for combined power.
Do not hide a violated combined lens power assumption inside an unexplained correction factor.
Using combined power beyond this page
Use extra internal precision to reverse-check Ptotal = P₁ + P₂, while the final reported combined power remains limited by the least certain input.
Record the operating condition, formula, units, and convention beside combined power. Those details distinguish a physically reproducible answer from a number copied out of context.
Continue from combined power
The next unknown may be handled by lens power calculator and diffraction grating wavelength calculator.
Continue only with a relationship whose physical scope matches the Combined Lens Power setup.
Checking the Combined Lens Power result
What does combined power represent?
It is the value of Ptotal = P₁ + P₂ under the units, field meanings, and optics assumptions printed on the combined lens power page.
How can combined power be checked?
Rearrange Ptotal = P₁ + P₂ to recover an entered value, reduce the surviving unit to D, and compare the scale with the physical setup.
Do the displayed units matter?
Yes. Convert each measurement to the unit beside its field before evaluating the combined lens power relationship.
Why might another combined power differ?
Another medium, temperature, geometry, reference frame, boundary condition, or sign convention can change the reported combined power.