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If the angular diameter of the moon be 3...

If the angular diameter of the moon be 30, how far from the eye a coin of diameter `2. 2c m` be kept to hide the moon?

Text Solution

Verified by Experts

The correct Answer is:
252 cm
Suppose the coin os kept at a distance r from the eye to hide the moon conpletely.
Let E be the eye of the observer and AB be the diameter of the coin.
Then, are AB = Diameter AB = 2.2 cm.
Now, `theta=30'=(30/60)^@=(1/2xxpi/180)^R=(pi/360)^R`
`:.theta=("Are")/("Radius")`
`orpi/360=2.2/r`
`or r=(2.2xx360)/picm`
`= (2.2xx360xx7)/22`
`=252cm`
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