The Spirit of Light

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Across
  1. 3. the return of light from a surface
  2. 7. allowing all light to pass through
Down
  1. 1. Allowing some light to pass through
  2. 2. change in direction of light when it passes from one medium to another obliquely
  3. 4. The range of wavelengths over which radiation extends
  4. 5. allowing no light to pass through
  5. 6. The natural agent that stimulates sight and makes things visible