Possible Clues:

• Triangular optical device
• Color refractor
• Piece of cut crystal, perhaps
• For a light turn-up for the knight with the Prime Minister around
• Triangular piece of glass, optical device
• Shape used to disperse light beams
• Solid figure - light separator
• Solid pair is married
• Governess is sort of solid
• Miss _____, governess in ¿he Importance of Being Earnest'