Rectilinear propagation of light
Rectilinear propagation of light states that light travels in a straight line
Materials: Three pieces of card, thread, candle.
Method:
Cut three rectangular pieces of card of the same size and label them A, B and C.
Make a hole in the center of each card. Pass a thread through holes.
Arrange the cards so that the holes are in a straight line.
A source of light for example a candle is placed behind the first card.
Card B is displaced slightly so that the cards are no longer in a straight line in diagram b.
Insert diagram
Observation:
The light can be observed through the card .When one card is slightly shift, the light is cut off from reaching an observer behind the third card. This is known as rectilinear propagation of light.