Concepts of Physics

IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

Locate the real image of a small object in a concave mirror just by seeing


Locate the real image of a small object in a concave mirror just by seeing.


The location of the image of an object in a concave mirror is given by the equation \(\frac{1}{v}+\frac{1}{u}=\frac{1}{f}\). To locate the image experimentally requires special skills. Usually in laboratories, parallax between another object and this image is used to locate it. In this experiment you will explore the possibility of at least approximately locating the image just by seeing at it.


A concave mirror with stand, scale, two pens in stands


  1. Place one pen with its tip on or slightly above the axis of the concave mirror.
  2. Make sure that the distance of the pen from the mirror is between \(f\) and \(2f\), closer to \(2f\) so that an inverted image is formed beyond the center.
  3. Bring your eye at appropriate place so that you are able to see the image.
  4. Gradually move the eye closer to the mirror and find the minimum distance from which you can see the image clearly.
  5. Measure the distance between your eye and the mirror in this case.
  6. Question: Is this the position of the image? Here is the ray diagram to help you answer this question. Check what happens if the eye is between the mirror and the image and if it is beyond the image.
  7. Locate the image by using the other pen in stand by removing parallax. You need not be very accurate as only an estimate is required. Explain if there is a difference between the location of the image determined by the pen and location of the eye from which the image can seen clearly


Figures to be made