7. The reflection of narrow beam of light from a plane mirror, falls normally on a metre rule placed vertical and at a distance of I m from the mirror. Calculate the angle of rotation of the mirror if the reflected beam is displaced 21.26 cm along the metre rule when the mirror is rotated. 8. A reflected ray in a mirror makes an angle of 30" with the incident ray. When the mirror is rotated 15", what angle will the reflected ray now make with the incident ray?
