( ( In contrast ) ( , ( ( a laser ) ( ( ( produces ( light ( in ( ( ( a ( ( very narrow ) ( wavelength band ) ) ) , ) ( so narrow ) ) ) ) ) ( that ( ( the laser ) ( is ( referred ( to ( ( ( ( ( as ( a monochromatic ) ) ( -LRB- ( ( one colour ) -RRB- ) ) ) , ) or ) ( ( ( single wavelength ) , ) source ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (NN contrast))) (, ,) (NP (DT a) (NN laser)) (VP (VBZ produces) (ADJP (JJ light) (PP (IN in) (NP (NP (DT a) (ADJP (RB very) (JJ narrow)) (NN wavelength) (NN band)) (, ,) (ADJP (RB so) (JJ narrow))))) (SBAR (IN that) (S (NP (DT the) (NN laser)) (VP (VBZ is) (VP (VBN referred) (PP (TO to) (NP (NP (NP (RB as) (DT a) (JJ monochromatic)) (PRN (-LRB- -LRB-) (NP (CD one) (NN colour)) (-RRB- -RRB-))) (, ,) (CC or) (NP (NP (JJ single) (NN wavelength)) (, ,) (NP (NN source)))))))))) (. .)))
In contrast, a laser produces light in a very narrow wavelength band, so narrow that the laser is referred to as a monochromatic (one colour), or single wavelength, source.
(ROOT (S (NP (PRP You)) (VP (VBP call) (NP (NP (DT a) (NN device)) (SBAR (WHNP (WDT that)) (S (VP (VBZ produces) (NP (NP (DT a) (ADJP (RB very) (VBN focused)) (NN beam)) (PP (IN of) (NP (NP (JJ visible) (NN light)) (PP (IN of) (NP (NP (RB just) (CD one) (NN wavelength)) (CC and) (JJ color) (NP (DT a) (NN laser)))))))))))) (. .)))