It is difficult to see through a closed glass window from the inside of a well lighted room, when it is dark outside. However it becomes relatively easy to see outside, when the light in the room are switched off explain.
This is because when the room is well lit the small portion of light that gets reflected by the surface of the glass pane is considerable as compared to the light coming from outside. This reflected light being more or equally intense makes it difficult to see the light coming from outside. When the list are switched off the opposite happens, i.e. the light from outside has more intensity and hence the outside world can be seen better