Leaving a light on in the bed room of married couples:
If a couple is leaving a light on in their house [on the night of Yom Kippur], then they are required to also leave a light on in their bedroom. This applies both in areas that are accustomed to light Yom Kippur candles at home, and in communities that are not accustomed to light Yom Kippur candles. [Thus, being that the custom today in all communities is to leave lights on in the home, therefore, a married couple is obligated to leave a light on at night in their bedroom. Seemingly, this candle is to remain lit throughout the night. Due to safety reasons, one should not light an actual candle, but rather simply turn on a lamp or night light that will remain lit throughout the night.]
On Erev Yom Kippur, a married couple must leave a light on in their bedroom.
If one’s wife is a Niddah must they light a candle in the room?
No. There is no need for a candle to be lit in their room. [However, some Poskim write that in areas accustomed to light Yom Kippur candles, which is all areas today, then they are likewise to leave a light on in the marital bedroom, even if the wife is in a state of Niddah.]
How long must the light remain on for in the bedroom?
The candle or lamp must remain lit until the morning.
Is leaving a night light on in the bedroom a valid form of light?
 Admur 610:2; Rama 610:1; Maharil Erev Yom Kippur p. 321; Mateh Efraim 610:2; Chayeh Adam 144:14; M”B 610:5; Nitei Gavriel 25:1; Shevach Hamoadim
Other opinions: The Magen Avraham 609/2 brings and justifies that the custom is to be lenient even in such a case, to not leave a light on in the bedroom, although he concludes to be stringent. Thus, Admur rules like the stringent conclusion of the Magen Avraham without making mention at all of a possibility for being lenient.
 The reason: As since one can see his wife due to the light that was left on, in the home, there is therefore suspicion that he may desire his wife and enter into the dark bedroom to perform marital relations. [If, however, one leaves a light on also in his bedroom, he will not come to sin.] [Admur ibid; Rama ibid; Maharil ibid] This means as follows: Even according to the custom that avoids lighting Yom Kippur candles, they agree that if they will regardless be seeing each other, then, in this situation, the best way to distance relations from occurring is to also leave a light on in their bedroom, being that its forbidden to have relations in the light. [Meaning, according to all we only say that not seeing each other is a greater form of distance from relations than leaving a light on, in a case that they will not see each other at all. However, if they will see each other anyways, then its best to leave the light on in the bedroom in order to at least have this form of distance from relations.]
 Admur ibid; M”B 610:4; Kaf Hachaim 610:5
 P”M 610 A”A 2; M”Z 1; M”B 610:5; Kaf Hachaim 610:6
 Shaar Hatziyon 610:4; Kaf Hachaim ibid
 Hisorerus Teshuvah 398; Nitei Gavriel 25:1
 Nitei Gavriel 25:1 footnote 1