A bulb is kept burning just right above the following solids. Name the shape of the shadows obtained in each case. Attempt to give a rough sketch of the shadow. (You may try to experiment first and then answer these questions).
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Solution
When an object is placed in the path of a ray of light, the object casts a projected image on the wall that intercepts the ray of light. Please note that this projected image is a two dimension figure on the wall. So, this project image will be the two dimensional version of the object in question.
A sphere will thus have a circle as its projected image. So the ball's shadow will be a circle. Hence item "A" from List I will be matched to item "2" A Circle in the list II.
A cylinder will have a rectangle as its projected image. So, the cylinder's shadow will be a rectangle. Hence item "B" from List I will be matched to item "1" A rectangle in the list II.
A book will have a rectangle as its projected image. So, the book's shadow will be a rectangle. Hence item "C" from List I will be matched to item "3" A rectangle in the list II.