A waveguide (40; 51 ; 61), arranged to guide light from at least one light source (53a-c), the waveguide comprising at least one guiding edge (43; 50a-c; 60) adapted to contain the light in the waveguide (40; 51 ; 61), and an extraction edge (44; 50d) adapted to enable extraction of the light from the waveguide (40; 51; 61), wherein the guiding edge (43; 50a-c; 60) is configured to reflect the light on its way towards the extraction edge (44; 50d). The guiding edge (43; 50a-c; 60) is further configured such that a direction (xrl, Xr2) of reflection of a ray of light impinging on the guiding edge (43; 50a-c; 60), in a given direction (xi) of incidence relative to a general direction (X0) of extension of the guiding edge (43; 50a-c; 60), is dependent on a position (P1, P2) of incidence along the guiding edge (43; 50a-c; 60). The waveguide may be configured such that virtually no light is lost through back-scattering or unintentional extraction or outcoupling through the at least one guiding edge.