The Total solution for NCERT class 6-12
You have learnt in the text howHuygens’ principle leads to the laws of reflection and refraction. Use the sameprinciple to deduce directly that a point object placed in front of a planemirror produces a virtual image whose distance from the mirror is equal to theobject distance from the mirror.
Let an object at O be placed infront of a plane mirror MO’ at a distance r (asshown in the given figure).
A circle is drawn from the centre(O) such that it just touches the plane mirror at point O’. According toHuygens’ Principle, XY is the wavefront of incident light.
Ifthe mirror is absent, then a similar wavefront X’Y’ (as XY) would form behindO’ at distance r (as shown inthe given figure).
can be considered as a virtualreflected ray for the plane mirror. Hence, a point object placed in front ofthe plane mirror produces a virtual image whose distance from the mirror isequal to the object distance (r).