After the 1st half-life 250 g of the radioactive material will be left.
<span>After the 2nd half-life 125 g of the radioactive material will be left. </span>
<span>After the 3rd half-life 62.5 g of the radioactive material will be left. </span>
<span>Therefore after 60 minutes, 3 half lives would have occurred. </span>
<span>Therefore the half-life = 60 / 3 = 20 minutes when 250 grams of the original material would have remained radioactive. </span>
<span>Therefore the answer is A) About 250 gram of the material decayed in 20 minutes.</span>
Answer: Since most sources of noise pollution are caused by essential machines, it is not possible to decrease the levels of sound.
Explanation:
Answer:
A. Galaxies
Explanation:
Galaxy cluster is known to contains 50 to 1000 galaxies, having a total mass between 100 trillion and 1 quadrillion solar masses, crossing across a distance of 30 million light years.
The word galaxy is derived from the Greek galaxias which means milky, a reference to the Milky Way. Galaxies range in size from the smallest of it with just a few hundred million stars to giants with one hundred trillion stars, with each rotating/orbiting its galaxy's center of mass.
