The invention provides a light emitting module (100) which comprises a light mixing chamber (101). The light mixing chamber comprises a base (102), at least one partly light transmissive side wall (103), an at least partly light transmissive-semi-reflective light exit window (104), a carrier (107), and at least one light emitting diode (105). The base (102) has a reflective inner surface (114). The at least one partly light transmissive side wall (103) extends from the base (102) towards the at least partly light transmissive, semi-reflective light exit window (104) which is arranged opposite to the base (102). The carrier (107) carries at least one light emitting diode (105) and is positioned at a distance (D1) from a nearest portion (108) of the at least one partly light transmissive side wall (103). The at least one light emitting diode (105) is arranged to emit source light (106) in a main direction different from 90 degrees with respect to the semi-reflective light exit window (104) and in the main direction away from the nearest portion (108) of the at least one partly light transmissive side wall (103) to enable subsequent mixing of the source light (106) within the mixing chamber (101) to generate mixed light (106′). The semi-reflective light exit window (104) and the at least one partly light transmissive side wall (103) are arranged to couple out source light (106) and mixed light (106′) as emitted light (106″). The mixing chamber has an inner mixing chamber width (W1) in the direction along the base (102) between the nearest portion (108) of the at least one partly light transmissive side wall (103) and an opposite portion (109) of the at least one partly light transmissive side wall (103) which is positioned opposite to the nearest portion (108) of the at least one partly light transmissive side wall (103). An inner mixing chamber height (H1) spaces the base (102) and the semi-reflective light exit window (104). The inner mixing chamber width (W1) and the inner mixing chamber height (H1) have an aspect ratio in the range of 4 to 15. The semi-reflective light exit window (104) has a reflectivity in the range from 30 to 80% for source light (106) and mixed light (106′). The distance (D1) from the at least one light emitting diode (105) to the nearest portion (108) of the at least one partly light transmissive side wall (103) is in the range from 5 to 30% of the inner mixing chamber width (W1).