The focal length of the objective of a compound microscope is `f_0` and its distance from the dyepiefe is L. The object is placed at a distance u from the objective. For proper working of the instrument.,

Options

A. `Lgta`
B. `Llta`
C. `Lgt2f_(0)`
D. `f_(0)ltLlt2f_(0)`

Answer

A, C

Explanation

We know that object is kept at a distance slightly greater than `f_(0)` from objective lens so that real image may be formed on the other side of the lens and then this image is observed with the help of convex lens known as eyepiece, To have magnification of objective lens greater than one we can place object anywhere between `f_(0) and 2f_(0)`. In this case image will be formed beyond `2f_(0)` and hence length of the tube must be even greater than `2f_(0)` to accommodate image formation from eyepiece. Now we can say that length of the tube must be greater than `2f_(0)` hence, option (c) is correct. Moreover, maximum possible value of a is `2f_(0)` and hence we can also say that length of the tube must always be greater than a. Hence, option (a) is also correct. Other two options are opposite and hence cannot be correct. Options (a) and (c) are correct.