The Flux Ratio Calculator helps you compare the intensity or brightness of two light or energy sources. It is commonly used in physics, radiometry, and astronomy to express the difference in output between two flux-emitting bodies—such as stars, lamps, or radiation sources. By inputting either their direct flux values or their magnitudes (in astronomy), this calculator provides a simple, accurate ratio that reflects how much more powerful one source is compared to the other.
This tool falls under the category of Radiometric and Photometric Calculators.
formula of Flux Ratio Calculator
Flux Ratio = F₁ / F₂
Where:
F₁ = Flux of source 1 (in any consistent units such as W/m², lumens, or photons/sec)
F₂ = Flux of source 2 (same unit as F₁)
If flux values are given in magnitudes (astronomical context):
Flux Ratio = 10^[(m₂ − m₁) / 2.5]
Where:
m₁ = Apparent magnitude of source 1
m₂ = Apparent magnitude of source 2
This logarithmic formula is useful in astronomy because star brightness is typically measured in magnitudes, not direct energy units.
Common Reference Table
| Term | Description |
|---|---|
| Flux (F) | Energy or light output per unit area per unit time |
| Apparent Magnitude (m) | Brightness of a star or light source as seen from Earth |
| Flux Ratio | Relative brightness or output comparison (unitless) |
| 1 W/m² | Standard unit of radiative flux |
| 1 lumen | Unit of luminous flux for visible light |
| 10^[(m₂ − m₁)/2.5] | Astronomical brightness ratio formula |
This table helps clarify frequently used terms across different applications of flux.
Example of Flux Ratio Calculator
Scenario 1: Direct Flux Values
Let’s say:
F₁ = 1000 lumens
F₂ = 250 lumens
Then:
Flux Ratio = F₁ / F₂
Flux Ratio = 1000 / 250
Flux Ratio = 4
This means source 1 emits four times more luminous flux than source 2.
Scenario 2: Using Magnitudes (Astronomy)
Suppose:
m₁ = 2.5 (brighter star)
m₂ = 5.0 (dimmer star)
Flux Ratio = 10^[(m₂ − m₁) / 2.5]
Flux Ratio = 10^[(5.0 − 2.5) / 2.5] = 10^(1) = 10
This means the brighter star emits 10 times more flux than the dimmer one.
Most Common FAQs
Flux is the total energy or light emitted, transferred, or received over a surface per unit time. It is often measured in watts per square meter (W/m²) or lumens.
A flux ratio provides a clear, unitless way to compare the strength or brightness of two sources, regardless of their absolute values, making it easy to interpret.
Yes, especially if you're comparing stars by their apparent magnitudes. The logarithmic flux ratio formula is standard in astronomy for this purpose.