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Changes caused by light


Changes in matter ] Importance of chemical reactions ] Chemical Reactions ] On-line practice ]

Examples where changes are due to light :

  • photosynthesis
  • photography
  • solar cells


  • Photosynthesis is a process whereby green plants make food in the presence of light, water, chlorophyll and carbon dioxide.
  • Food produced by leaves is in the form of glucose ( a simple sugar ) which is then converted to and stored as starch in leaves. 
  • The food stored in leaves is the source of food for all living things.


  • The different intensity of light that falls on the light-sensitive film paper causes different shades to form.
  • The film is sensitive because it is coated with an emulsion consisting of grains of silver salt suspended in gelatine.
  • When light falls on the silver salt, the silver salt decomposes into silver, which produces the dark areas on the film.
Solar cells
  • Solar cells are made from elements such as silicon or selenium.
  • They can convert sunlight directly into electricity.

Changes caused by heating ] [ Changes caused by light ] Changes caused by mixing ] Changes caused by electricity ]