Index of refraction for any material = speed of light /speed of light in the material.
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Answer: The reason why most metal sink is because the is water is pushing the metal down to the ground and which can not be lifted up but the lighter the objects float back to the surface.
Explanation:
<u>Answer</u>
1/4
<u>Explanation</u>
half life = 15 years
decay period = 30 years
The number of half-lives = 30 ÷ 15
= 2 half lives
1 ⇒(<em>after 1st half life</em>) ⇒ 1/2 ⇒ (<em>after 2nd half life</em>) ⇒ 1/4
The fraction that remained is 1/4.