3. What would be the actual size of an object that appears as 2 µm when it is magnified 1000 times?
Correct Answer: A. 2 nm
Actual size = Image size ÷ Magnification = 2 µm ÷ 1000 = 0.002 µm = 2 nm
## Option Analysis
A. 2 nm
Image size = 2 µm at 1000× magnification. Actual size = image size ÷ magnification = 2 µm ÷ 1000 = 0.002 µm. Convert: 0.002 µm × 1000 = 2 nm (correct).
B. 20 nm
This implies 10× magnification (2 µm ÷ 0.1 µm = 20 nm), not 1000×, so incorrect.
C. 2 mm
This assumes demagnification (2 µm × 1000 = 2 mm), opposite of microscopy enlargement. Incorrect.
D. 20 µm
Actual size larger than image violates magnification principle (should shrink when dividing). Incorrect.
### Magnification Formula
Actual size = Image size ÷ Magnification
### Unit Conversions
- 1 µm = 1000 nm
- 1 nm = 10-9 m (nanoscale for viruses, DNA)
### Common Pitfalls in Exams
| Option | Calculation Error | Why Wrong |
|---|---|---|
| A. 2 nm | 2 µm ÷ 1000 | Correct |
| B. 20 nm | ÷ 100 nm | Wrong divisor |
| C. 2 mm | × 1000 | Reverse operation |
| D. 20 µm | ÷ 0.1 | Ignores 1000× |
#GATE Life Sciences Tips
Practice: E. coli ~2 µm actual appears 2000 µm at 1000×. Master nm/µm conversions for PYQs.
