Question

Rajesh conducts the following experiment.
He cuts $3$ cardboard pieces, each with a hole in the center, and aligns them in a straight line as shown in the image. He now puts a candle in front of the first cardboard piece and looks at it from behind the third piece. He is able to see the candle. He puts the third cardboard piece aside and now tries to look at the candle. But this time, he is not able to see it.
What can be concluded from this experiment?

• A. The visibility of the candle depends on the position of the candle with respect to Rajesh
• B. The visibility of candle depends on the position of Rajesh
• C. The visibility of candle depends on the relative alignment of $3$ cardboards
• D. The candle is visible only when the $3$ cardboards are in a line because light from the candle travels only in a straight line, to reach Rajesh's eyes.

Answer 1

Answer: (D)

The candle is visible only when the $3$ cardboards are in a line because light from the candle travels only in a straight line, to reach Rajesh's eyes.

Light travels in a straight line, called a ray which represents the direction of light propagation until it is not obstructed by some other particles or medium. This phenomenon is called the rectilinear propagation of light.