Which of the following combinations yields approximately 400x total magnification?

• A. X10 ocular with X40 objective
• B. X4 ocular with X100 objective
• C. X20 ocular with X20 objective
• D. X8 ocular with X50 objective

Answer: (A)

Total magnification is the product of the ocular (eyepiece) magnification and the objective magnification. For about 400x, the standard, practical setup is a 10x ocular with a 40x objective, giving 10 × 40 = 400x. This combination is commonly used because it provides a good balance of magnification, brightness, and a reasonable field of view for routine histology viewing.

Other pairs also multiply to 400x in theory, but they’re less typical in routine practice. A 4x ocular with a 100x objective uses an oil immersion objective and is not the usual choice for quick scanning or routine slides. A 20x ocular with a 20x objective can work too, but it reduces the field of view and is not as commonly employed. An 8x ocular with a 50x objective is uncommon and awkward to use in many lab setups.