| Date | May 2013 | Marks available | 1 | Reference code | 13M.1.HL.TZ1.3 |
| Level | Higher level | Paper | Paper 1 | Time zone | Time zone 1 |
| Command term | Question number | 3 | Adapted from | N/A |
Question
The diatom Didymosphenia geminata is a species of single-celled alga that lives in warm, shallow water. In the light microscope image below, the scale bar is equal to 10 micrometres (10 μm). What is the actual length of the cell?
A. 0.007 mm
B. 0.07 mm
C. 0.7 mm
D. 7.0 mm
Markscheme
B
Examiners report
Question 3 was answered much less successfully than expected. Some teachers reported on G2 forms that it was too difficult without calculators, but the math was in fact very easy. A large number of candidates were unable to convert 70µm into 0.07mm by moving the decimal point three places to left. Students should be taught that S.I. units are increased by a factor of 1000 so conversion from micrometres to millimetres is accomplished by dividing the length by 1000.
