On a dark night Harish and Priyanka were sitting together. Harish was watching movie while his wife Priyanka was reading mystery book.Suddenly the power went out and Harish decided to go to bed, but strangely Priyanka kept on reading.
There was no artificial light around, Priyanka kept on reading.
How come ?
Priyanka was blind and she was reading book by Braille.