A radioactive isotope has a half-life of 2 minutes. How many total minutes will it take for 100-g of the isotope to get to just 6.25-g remaining

It would take 12 minutes.

8 minutes

Explanation:

G(g)                 T(min)

100 0

502

25 4

12.5    6

6.25 8

     another    way:

100/6.25 = 16

  16 = 2⁴       ( 4 half lives)    

Each half life is 2 minutes

so 4 half lives will be 8 minutes

on passing the small ampere of electric current through the tube made of ar and hg of cfl generates uv rays which excites the fluorescent and thus emits the high radiation by consumption of just 5- 12 w in comparison to incandescent light which requires more power such as around 40 - 55 w to lighten.

moreover the life span of fluorescent or cfl is around 8000 h whereas the life span of incandescent is around 1200 h

hence, the building installed with incandescent lights bears more electricity bill.