Question

when one enter setting lightroom from bright light one is unable to see the objects in the dim light room for some time why

Answer 1

because the pupils are small enough in bright light but in dim light they become large after sometime...
it takes time for them to become large

Answer 2

The reason for this is that in bright light the size of pupil of our eye is small. When we enter the dark room, due to small size of pupil, very little light enters our eyes. But after some time, the pupil expands & we are able to see things as more light enter our eyes now.

and the same way, while coming out from a dark room to bright light, our eyes feel a glaring affect. This is due to the reason that in dark room the pupil is large so when we come out in bright light, a large amount of light enters our eyes and we feel glare. But after sometime, the pupil contracts and we become able to see clearly as less light enters our eyes now.