True regarding the use of head mirror is/are?

Answer- A. Applied on right eyeTwo types of illumination is used in otolaryngologcial examination:Semi mobile illumination like the Bull's lampMobile illumination like the Clair's head light, or cold light based head bands.Bull's lamp: is a semi mobile source of illumination.The approximate focal length of the mirror is about l0 inches.The mirror is fured over the right eye in such a way pa of the mirror touches the nose.The minor is adiusted while keeping the left eye closed and the right eye is kept open to focus. Then both eyes are opened while examining.