Which of the following statements about optical microscope is/are correct? 1. Both the eyepiece and objective of a microscope are convex lenses. 2. The magnification of a microscope increases with increase in focal length of the objective. 3. The magnification of a microscope depends upon the length of the microscope tube, 4. The eyepiece of a microscope is a concave lens. Select the correct answer using the code given below.

An optical compound microscope utilizes two sets of lenses: the objective and the eyepiece. Both are convex (converging) lenses. The objective lens forms a real, inverted, and magnified image of the specimen, which then acts as the object for the eyepiece. The eyepiece functions as a simple magnifier to produce a final virtual image. The total magnification (M) of a compound microscope is approximately given by M = (L/f_o) * (D/f_e), where L is the tube length, f_o is the objective focal length, f_e is the eyepiece focal length, and D is the least distance of distinct vision. Consequently, magnification is directly proportional to the tube length (L) and inversely proportional to the focal length of the objective (f_o). Therefore, magnification increases as the focal length of the objective decreases, making statement 2 incorrect and statements 1 and 3 correct.