Luminosity at frequency 150 MHz as a function of the source axial size for different jet powers L₀: 10⁴⁰ W (blue), 10³⁹ W (orange), 10³⁸ W (green), 10³⁷ W (red), 10³⁶ W (purple) and 10³⁵ W (brown). LOFAR catalogue radio galaxies are represented by black points and the 3C catalogue sources by red points. The pink lines indicate isochrones for 0.5 Myr (solid), 5 Myr (dashed), 50 Myr (dot-dashed), and 500 Myr (dotted).