You have learnt in the text how Huygens’ principle leads to the lawsof reflection and refraction. Use the same principle to deduce directlythat a point object placed in front of a plane mirror produces avirtual image whose distance from the mirror is equal to the objectdistance from the mirror.
According to the Huygens principle, the light is made up of waves that vibrate up and down in the direction perpendicular to the direction in which the light travels.
Let an object is placed in front of a plane mirror as shown in the figure below.
Figure (1)
Object is placed at point O and a circle touching mirror at O ′ is drawn from point O, AB is the wave front of the incident line. If mirror is not present, then the similar wave would be formed behind O ′ . Thus, the centre of the reflected wave front is observed at the same distance from the mirror as the object.
Figure (2)
Here A ′ B ′ is the reflected ray of the mirror.
Hence, the distance between the rays is same. Thus, the object placed in front of the mirror creates a virtual image such that the image distance is equal to the object distance.
According to the Huygens principle, the light is made up of waves that vibrate up and down in the direction perpendicular to the direction in which the light travels.
Let an object is placed in front of a plane mirror as shown in the figure below.
Figure (1)
Object is placed at point O and a circle touching mirror at
Figure (2)
Here
Hence, the distance between the rays is same. Thus, the object placed in front of the mirror creates a virtual image such that the image distance is equal to the object distance.
