If a couple by accident left the bedroom light on during shabbos. Can the couple have relations in that room during the evening if there is no other private room?
It is forbidden to have relations in the light. However, the light can be covered over with a rag (or something that won’t catch fire), and it would then be permitted to have relations in the room.
Sources: Ramban, Issurei Biah 21:10; Shulchan Aruch, Orach Chaim 240:12, Yoreh De’ah 25:5 (the actual prohibition); Chasam Sofer, Orach Chaim 73 (the possibility of covering the light). The Gemara discusses the possibility of erecting a partition between the light and the bed, but this is forbidden to do on Shabbos itself, unless one finds a non-Jew to do it for you. It is generally more practical to try to cover up the lamp or light.