Free · Physics models
Radiation Pressure From Luminosity and Temperature
Estimate pressure from isotropic radiation at a surface and the isotropic thermal radiation pressure.
- Formula & worked example
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Calculator inputs
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How to use this calculator
- Enter the known values in the units shown. Results update as you type.
- Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
- Use the worked example to check the method. Reset restores the starting fields.
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Formula and method
At 300 K, the retained radiation constant gives thermal radiation pressure about 2.04276 µPa.
psurface = s L cos²θ/(4π r² c); pthermal = a T⁴/3.
Worked example
Enter these known values and leave the other values blank.
- Source luminosity (total emitted power)
- 1 L☉
- Distance
- 1 au
- Temperature
- 300 K
- Pressure
- 4.54 μPa
- Isotropic thermal radiation pressure
- 2.043e-15 GPa
Assumptions and limitations
- Luminosity is total source power, despite the retained internal field name solar_constant. Irradiance follows inverse-square dilution.
- The surface factor is one for ideal absorption and two for ideal specular reflection; pressure denotes the normal momentum transfer.
- The retained radiation constant is 7.565767 × 10⁻¹⁶ J/(m³·K⁴). Temperature is absolute; surface angle is restricted to 0–90°.
- Enter known quantities and clear the unknown to use available inverse branches. Locks retain supplied values. Consistency messages cover fully visible equations; identities with hidden dependencies may require a manual consistency check. Preset values are illustrative approximations, and unit selectors preserve the underlying quantity.
Common questions
How do I solve for a different quantity?
Clear that quantity and supply enough independent known values. Some outputs are one-way or tied to a selected preset, so they cannot determine every input.
References
Explicit physical domains for retained model.