Question

9. (2 points) The angular size of a full moon is 0.5º. The diameter of a penny is 19 mm. What is the maximum distance from your eye that you can hold a penny and still have it completely block out the full moon?

Answer 1

Solution:

Angular size =0.5^o

Diameter of the penny=19 mm =19 X 10^-3 m

From the diagram, triangle ABC,

$tan (\theta )= \frac{AB}{BC}$

$tan (0.5^{o} )= \frac{19\times 10^{-3}m}{BC}$

$BC=\frac{19\times 10^{-3}m}{8.72\times 10^{-3}}$

$BC=2.17m$

BC is the maximum distance that we can hold the penny from eye.

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