A 128 gram Radium-226 sample with a half-life of 2.25 billion years is found. How many grams will remain after two half-lives? A 16 grams
B.32 grams
C.64 grams
D.128 grams

Option B. 32 g

Explanation:

From the question given above, the following data were obtained:

Original amount (N₀) = 128 g

Half-life (t½) = 2.25 billion years

Number of half-lives (n) = 2

Amount remaining (N) =?

The amount of 128 gram of Radium-226 that will remain after 2 half-lives has elapsed can be obtained as followb

N = 1/2ⁿ × N₀

N = 1/2² × 128

N = 1/4 × 128

N = 0.25 × 128

N = 32 g

Therefore, 32g of the sample will remain.

5 w for 1hr = 5x60x60 joules=300x60=3000x6=18,000j as total energy conversion. efficiency of bulb needed for radiant to thermal within 18000

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