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Date	May 2019	Marks available	1	Reference code	19M.1.HL.TZ1.9
Level	Higher level	Paper	Paper 1	Time zone	Time zone 1
Command term	Identify	Question number	9	Adapted from	N/A

Question

Which wavelength of electromagnetic radiation is absorbed efficiently by chlorophyll for photosynthesis?

A. 45 nm

B. 45 μm

C. 450 nm

D. 450 μm

Markscheme

Examiners report

This was another question that was criticised for testing what was considered by some to be pointless factual recall. Only 40 % of candidates correctly identified the wavelength of light that chlorophyll absorbs but the discrimination index was very high. Two of the answers could have been eliminated if candidates knew that the wavelengths of light are measured in nanometres not micrometres. The two answers remaining were 45 nm and 450 nm. Any candidate who remembered that the spectrum of visible light and also of absorption by chlorophyll is from 400 to 700 nm could easily have chosen the correct answer. In the examiners’ view the spectrum of visible light and the units used to measure light wavelengths are useful pieces of information and not pointless facts.

Syllabus sections

Core » Topic 2: Molecular biology » 2.9 Photosynthesis

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