Optical device (4)
'optical device' is the definition.
(lens is a kind of optical device)
This is the entire clue.
(Other definitions for lens that I've seen before include "Bender of beams" , "Camera component" , "Optical refractor" , "Aid for viewing" , "Photographer's accessory" .)
'optical device' is the definition.
(laser is a kind of optical device)
This is all the clue.
(Other definitions for laser that I've seen before include "Optical device producing an intense beam of light" , "Device that generates an intense ray of light" , "Beam (used in surgery)" , "modern light industry" , "Light amplification by stimulated emission of radiation" .)
'optical device' is the definition.
(prism is a kind of optical device)
This is the entire clue.
(Other definitions for prism that I've seen before include "Optical device used to deviate a beam" , "Transparent block" , "Refracting body" , "It breaks light up into rainbow's colours" , "Light-refracting element" .)