PROPAGATION OF LIGHT : PHYSICS

PROPAGATION OF LIGHT : PHYSICS

#1.Light travels along straight lines in a medium or in vacuum. The path of light changes only when there is an object in its path or where the medium changes. We call this rectilinear ( straight-line ) propagation of light.

#2.Light that starts from a point A and passes through another point B in the same medium actually passes through all the points on the straight line AB. Such a straight-line path of light is called a ray of light. 

#3.Light rays start from each point of a source and travel along straight lines till they fall on an object or a surface separating two media (mediums). A bundle of light rays is called a beam of light.

#4.A part from vacuum and gases, light can travel through some liquids and solids. A medium in which light can travel freely over large distances is called a transparent medium. Water, glycerine, glass and clear plastics are transparent. 

#5.A medium in which light cannot travel is called opaque. Wood, metals, bricks,etc.,are opaque. 

#6.In Materials like oil, light can travel some distance, but its intensity reduces rapidly. Such materials are called translucent.