the hooked member 162 includes a generally u shaped portion 1622 and a connection portion 1624 the u shaped portion 1622 is configured for slidably engaging with the flange portion 14 a that is the u shaped portion 1622 is slidable along the flange portion 14 a the u shaped portion 1622 extends from an outer side of the connection portion 1624 preferably the connection portion 1624 is integrally formed with the u shaped portion 1622 with the u shaped portion 1622 and the connection portion 1624 being parts of a single continuous body of material the connection portion 1624 is parallel to and faces the round opening 142 an inner side of the connection portion 1624 is connected with the optical sheet 164 the position of the optical sheet 164 in the round opening 142 can be changed by sliding the u shaped portion 1622 along the flange portion 14 a the optical sheet 164 has an area less than that of the round opening 142 in the illustrated embodiment a diameter of the optical sheet 164 is less than half a diameter of the round opening 142 the optical sheet 164 is parallel to and faces the round opening 142 and covers a region m thereof the region of the round opening 142 not covered by the optical sheet 164 is defined as a region n in this embodiment the optical sheet 164 is a diffuser the indoor lamp 10 is used for example with a desktop 200 the indoor lamp 10 is positioned over the desktop 200 and the optical sheet 164 faces the desktop 200 light emitted from the light source 12 does not directly reach the eyes of a user 202 due.