Following data was recorded for values of object distance and the corresponding values of image distance, in the study of real image formation by a convex lens of power `+ 5 D`. One of these observations is incorrect. Identify and give reason :
`{:("S.No",1,2,3,4,5,6),("Object distance (cm)",25,30,35,45,50,55),("Image distance (cm)".97,60,37,35,32,30):}`

Explanation

Here, `P = + 5 D`
`f = (100)/(P) = (100)/(5) = 20 D`
In observation 3, where `u = 35 cm`, object lies between `f and 2 f`. The image must be beyond `2 f` i.e., `v gt 40 cm` But `v = 37 cm` i.e., image also lies between `f and 2 f`, which is wrong.