i have read in my 7th grade text book, "LIGHT TRAVELS IN STRAIGHT LINE". But in my 12th grade text book, it has been mentioned " Light is an electromagnetic wave and transverse in nature". Transverse means the vibrations are perpendicular to the direction of propagation. Which is true? If light is a transverse wave, then it will have crest and trough which is not straight lines, but curves. Could u please elaborate me, revered members?