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First exams 2025

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Absorption Spectra (SL IB Biology)

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Absorption Spectra

  • Light is made up of a mixture of all the visible wavelengths to include red, orange, yellow, green, blue, indigo and violet
  • An absorption spectrum is a graph that shows the absorbance of different wavelengths of light by a particular pigment in the chlorophyll
  • Within the chlorophyll, light energy results in the excitation of electrons which triggers transfer of electrons leading to a series of reactions which make up the process of photosynthesis
    • During photosynthesis, light energy is transformed to chemical energy when glucose is formedĀ 
  • Chlorophylls absorb wavelengths in the blue-violet and red regions of the light spectrum
  • Carotenoids absorb wavelengths of light mainly in the blue-violet region of the spectrum
  • The chemical structure of these molecules determines the wavelengths of light that can be absorbed
  • The green part of the spectrum is largely reflected from the leaf and this is why leaves usually appear green

Absorption spectra of chlorophylls and carotenoids_1, downloadable AS & A Level Biology revision notes

Absorption spectra of chlorophyll A, chlorophyll B and carotenoid pigments

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Ruth

Author: Ruth

Expertise: Biology

Ruth graduated from Sheffield University with a degree in Biology and went on to teach Science in London whilst also completing an MA in innovation in Education. She gained 10 years of teaching experience across the 3 key science disciplines and physical education. Ruth decided to set up a tutoring business to support students in her local area. Ruth has worked with several exam boards and loves to use her experience to produce educational materials which make the mark schemes accessible to all students.