Abstract I present here a short personal view of our understanding of the Chandra detected knots and hot spots of powerful Fanaroff Rilley (FR) II radio galaxies and quasars in the context of leptonic models. Observations of the knots and hot spots strongly suggest that the jets in these powerful sources retain their relativistic velocities at large scales, all the way to the hot spots. The emission mechanism suggested for the knots of quasars and FR II radio galaxies is external Compton (EC) off the cosmic microwave backgounrd (CMB) from a relativistic flow, while for the hotspots Upstream Compton (UC) scattering from a decelerating relativistic flow.
Keywords radiation mechanisms: non-thermal -galaxies: quasars
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