# Physics - General Knowledge Questions and Answers

 If the time taken for hearing the echo of a girl's voice after reflection from a cliff is 6 seconds, calculate the distance of the girl from cliff ? A) 660 m B) 1980 m C) 330 m D) 990 m Correct Answer : 990 m Explanation :let girl is standing on A, then sound goes to the B cliff and then come back to A before she hear the sound. time=6 sec, speed OF voice/sound=330 m/s now, distance(AB+BA)= speed*time = 330*6 =1980 m distance between the cliff = AB = BA AB+BA = 1980 2AB = 1980 AB = 990 m hence the distance of the girl from cliff 990 m A dynamo converts ? A) electrical energy to mechanical energy B) electrical energy to magnetic energy C) chemical energy to electrical energy D) mechanical energy to electrical energy Correct Answer : mechanical energy to electrical energy Explanation :dynamo in Electrical Engineering A dynamo is a device for converting mechanical energy into electrical energy. In a dynamo, the mechanical energy of rotation is converted into electrical energy in the form of a current in the armature. It is an electrical generator that creates direct current(DC) If the angle of incidence formed by a ray of light on a plane mirror is 37°, then the angle of refraction is? A) 53° B) 143° C) 37° D) 90° Correct Answer : 37° Explanation :law of reflection - the angle of incidence is equal to the angle of reflection. The most comfortable distance at which one can read with a normal eye is: A) 25 cm B) 20 cm C) 15 cm D) 10 cm Correct Answer : 25 cm Explanation :The most comfortable distance at which one can read with a normal eye is about 25 cm.