Evan's Space

Wonders of Physics


Light – Two mirrors in parallel

The diagram below shows a object O placed at the middle of two parallel mirrors. Which of the following is not a possible position of image of O?


Solutions: Option D

Based on the concept of characteristics of mirror image – Distance of object to mirror is equal to Distance of image to mirror.

Object O at the centre of two mirrors, based on the above characteristic, B and C are possible positions of image of O.

Consider A. Treating C as the object now and using the mirror on the left, distance of C to left mirror is equal to distance of A to left mirror.

Hence A is a possible position of image of O.

Consider D. Treating B as object and using the mirror on the right, distance of B to right mirror is not equal to distance of D to right mirror.

Hence D is not a possible position of image of O.



N2007P1Q20 Light – Mirror Image through Periscope

The diagram shows an object O viewed using two mirrors. A person looks into the mirrors as shown. At which position is the image of O seen.periscopeSolutions: Option D

To solve this kind of question, you have to do in stages.

1) Consider the object O and the mirror at the top. The image formed will be equal distance perpendicular to the mirror (follows the 5 characteristics of mirror image). Let the image be O’.

2) Now treat O’ as the new object and consider the mirror at the bottom.  Likewise apply the same principle, the image of O’ is now at position D. Alternatively, a fast and simple way is based on the concept that to our eyes, light seems to travel in straight line. Hence to our eyes, the image of O is directly in front.