how to find index error in optics experiment of finding the focal lenght of the lens by uv method ?

This can be found by this: 

    1.Using the central length gotten by removed protest strategy set the estimations of u (separation amongst mirror and question) going from 1.5f to 2.5f. Separate the range into various equivalent strides. 

    2.Place the mirror before an enlightened wire cloth. It goes about as the protest. 

    3.Now, settle the mirror at the separation u (which is gotten as 1.5f) from the wire dressing. 

    Place the screen on the table confronting the mirror such that the thought about picture lies the screen. 

    We can alter the position of the screen to get the reasonable picture of the wire dressing. 

    Keeping the separation amongst question and mirror settled, modify the position of screen keeping in mind the end goal to get the unmistakable picture of the protest. 

 

    Calculate the central length of the given sunken mirror by utilizing the connection, f = uv/(u+v). 

    Repeat the trial for various estimations of u (up to 2.5f) and in each time, measure v and record it in the forbidden segment. 

    Calculate the central length (f) of the curved mirror each time.