48. That is, at that time they will not realize that they had been dead and had been raised back to life after a long period, but they will be thinking that they had fallen asleep, and had been woken up suddenly by some terrible catastrophe, and were running away from it. (For further details, see Surahs (TaHa, Ayat 103); (Al-Hajj, Ayats 1-2).
49. Here, it is not clear as to who will give this answer. It may be that they themselves would realize after some time to their horror that it was the same thing of which the Messengers of God used to inform them and they used to belie them. It may also be that the believers will remove their misunderstanding and tell them that it was not waking up from sleep but the second life after death. And it may also be that they will understand this from the general conditions prevailing on the Day of Resurrection and the angels might tell them this.