Converging mirrors facing each other

[jsalapide]

two converging mirrors A & B, having focal lengths 12 cm and 4 cm respectively, are facing each other and 36 cm apart on a common principal axis. A plastic sword is placed vertically upward in front of mirror A at a distance of 18 cm. Locate and describe the nature, orientation and size of the image formed by the combination of mirrors if the 12 cm mirror is the first reflector and reflection of light occurs only once on the surface of the mirrors.

First, I let the mirror A as the first reflector, I solved for q1 and I got 36. Therefore its a real image.

After that, I let the 2nd image at mirror B. To solve for p, I used p = d-q1, where d is the distance between the 2 mirrors. I got 0.

Is it possible for p to be zero? help..

 

[rl.bhat]

Yes. It is possible. A very small section of the any mirror acts like a plane mirror for which the object distance is the equal to image distance.