photochromic

• What are photochromic pigments used for?

  To change colour in ultraviolet light
• How do spectacles with photochromic film react to sunlight?

  They automatically darken as sunlight increases
• In what type of buildings are photochromic pigments particularly useful?

  High-rise buildings and office blocks
• Why are photochromic pigments beneficial in buildings?

  They prevent strong sunlight from penetrating inside