A person in a dark room looking through a window can clearly see a person outside in the daylight, where as the person outside cannot see the person inside. Why ?

What happens if a person sleeps outside in mid winter ?

A person crossing a road with a certain velocity due north sees a car moving towards east The relative velocity of the car w.r.t the person is sqrt(2) times that fo the velocity of the persons. The angle made by the relative velocity with the east is

A concave mirror has a focal length of 25 cm. A person wants to see his face in this mirror, at what distance should the person stand ?