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.