Chapter 27, Problem 62A

To determine

To determine the height above the ground is an opening that casts a spot of 15cm in diameter.

Explanation of Solution

Introduction:

The circular spots observed just before and after the eclipse. Because the tiny gaps between leaves act as pinhole lenses projecting crescent shaped images of the eclipsed sun on to the earth.

Generally, the circular spots appear before and after the eclipse and they are cast with tree leaves and they act like a camera. As given, that to cast a 10 cm diameter spot on the ground the opening is 100 times higher and at the height of 10 m above the ground. Similarly, to cast the 15 cm spot with the opening of 100 times higher the spot would be cast with 15 m above the ground.

Conclusion:

The 15 cm spot cast by opening at 15 m above the ground.