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.
1 and 3
3 only
3 and 4
1, 2 and 4
Answer is Wrong!
Answer is Right!
This question was previously asked in
UPSC CAPF – 2018
Statement 2 is incorrect: The magnification of the objective lens is inversely proportional to its focal length. A shorter focal length objective provides higher magnification (and typically lower depth of field and working distance).
Statement 3 is correct: The overall magnification of a compound microscope is approximately the product of the magnification of the objective and the magnification of the eyepiece. The magnification provided by the objective is related to the distance between the objective and the intermediate image (which is determined by the microscope’s tube length) and the focal length of the objective. Thus, the length of the microscope tube affects the magnification.
Statement 4 is incorrect: As mentioned in statement 1, the eyepiece acts as a magnifying glass, which is achieved using a convex lens or a combination of lenses that function as a convex lens.