What is the filter area for a 37 mm cassette?

• A. 0.00785 mm^2
• B. 855 mm^2
• C. 385 mm^2
• D. 1.234 mm^2

Answer: (A)

The important idea is that the filter area is the area of a circle, so you use A = πr^2. The diameter is 37 mm, so the radius is r = 37/2 = 18.5 mm. Plugging in: A = π × (18.5 mm)^2 ≈ 3.1416 × 342.25 ≈ 1075 mm^2. That means the filter opening covers about 1075 square millimeters.

The options shown don’t match this calculation; the value 0.00785 mm^2 corresponds to a radius of only about 0.05 mm, which isn’t plausible for a 37 mm cassette. This suggests a misprint or unit mismatch in the choices. The correct method yields roughly 1075 mm^2, so always verify units and the stated diameter when doing these calculations.