Radioactive Decay Math Quiz

A soil sample near Chernobyl was found to contain 100 kBq/m of iodine-137. If the half-life of iodine-137 is approximately 25 years, how much cesium-137 will remain in the sample after 75 years?

• 12.5 kBq/m

• 25 kBq/m

• 50 kBq/m

• 100 kBq/m

A sample of radioactive waste has a half-life of 5 years and an activity level of 4 curies. After how many years will the activity level of this sample be 1 curie?

• 5 years

• 10 years

• 15 years

• 20 years

The half-life of radon gas is approximately 7 days. Two weeks after the introduction of radon into a sealed room, the fraction of the original amount remaining is closest to:

• 1/4

• 1/2

• 1/8

• 1/16

What is the estimated energy cost per year for a 9W LED bulb providing 800 lumens?

• $1.26

• $6.02

• $3.50

• $2.00

What is the estimated energy cost per year for a 43W halogen bulb providing 800 lumens?

• $6.02

• $1.26

• $4.50

• $3.00

How many watts does a comparably bright LED bulb use compared to a 40 watt incandescent bulb?

• 12 watts

• 40 watts

• 20 watts

• 25 watts

What is the brightness in lumens for both the 9W LED and 43W halogen bulbs?

• 800 lumens

• 600 lumens

• 1000 lumens

• 500 lumens

What is the efficiency percentage of incandescent light bulbs?

• 10%

• 90%

• 50%

• 75%

How many hours do LEDs last compared to traditional incandescent bulbs?

• 50,000 hours

• 2,000 hours

• 10,000 hours

• 5,000 hours

How many hours do traditional incandescent bulbs last?

• 2,000 hours

• 50,000 hours

• 10,000 hours

• 5,000 hours