Suppose there are 100,000 atoms of a radioactive substance that has a ½ life of 10 minutes. How many atoms will remain after 40 minutes: a. 2,500
b. 10,000
c. 12,500
d. 50,000

Show calculation

c. 12,500

Explanation:

Original number of atoms = 100,000 atoms

Half- life  = 10min

Unknown:

The number of atoms that will remain after 10min  = ?

Solution:

The half - life is the time taken for half of a radioactive substance to decay by half.

    Time taken        Number of atom   half life

           10min             100000                   _

           20min             50000                    1

           30min             25000                    2

           40min              12500                     3

wind moving at higher speeds will transfer more energy to the water, resulting in stronger waves.

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