Magnification scales actual size by the given factor

Steps:

• Actual diameter is 1 μm.
• Multiply by magnification: 1 μm × 50,000 = 50,000 μm.
• Convert to mm: 50,000 μm ÷ 1,000 = 50 mm.
• This is the diameter shown in the micrograph.

Why C is correct:

• Magnification formula states image size = actual size × magnification factor, yielding 50 mm directly.

Why the others are wrong:

• A: 0.5 mm equals 500 μm, under-magnified by factor of 100.
• B: 5 mm equals 5,000 μm, under-magnified by factor of 10.
• D: 500 mm equals 500,000 μm, over-magnified by factor of 10.

Final answer: C