( ( If ( ( the light ) ( ( hits ( the ( glass surface ) ) ) ( at ( an ( oblique angle ) ) ) ) ) ) ( , ( ( the slowing ) ( ( causes ( ( ( the ( light ( beam ( to bend ) ) ) ) , ) ( ( a phenomenon ) ( known ( as refraction ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN If) (S (NP (DT the) (NN light)) (VP (VBZ hits) (NP (DT the) (NN glass) (NN surface)) (PP (IN at) (NP (DT an) (JJ oblique) (NN angle)))))) (, ,) (NP (DT the) (NN slowing)) (VP (VBZ causes) (NP (NP (DT the) (JJ light) (NN beam) (S (VP (TO to) (VP (VB bend))))) (, ,) (NP (NP (DT a) (NN phenomenon)) (VP (VBN known) (PP (IN as) (NP (NN refraction))))))) (. .)))
If the light hits the glass surface at an oblique angle, the slowing causes the light beam to bend, a phenomenon known as refraction.
(ROOT (S (NP (VBG Slowing)) (ADVP (RB down)) (VP (VBZ causes) (ADJP (JJ light) (S (VP (TO to) (VP (VB refract)))))) (. .)))