Possible Clues:

• A dispersive one is commonly triangular
• Cut-glass object teacher put up in the course of the afternoon
• Transparent object that refracts light
• Optics prop
• Solid moral support is required possibly when starting over
• Binoculars component
• Light-refracting crystal
• Light-refracting element
• Glass triangle that separates white light into the colour spectrum
• White light splitter