The technetium isotope 99Tc is useful in medical imaging, but its short 6.0 h half-life means that shipping it from a source won't work; it must be created where it will be used. Hospitals extract the 99Tc daughter product from the decay of the molybdenum isotope 99Mo. The 99Mo source has a half-life of 2.7 days, so it must be replaced weekly. A hospital receives a 20 GBq 99Mo source.

What is its activity one week later?

Express your answer using two significant figures.

Explanation:

Initial radioactivity =  20 GBq

half life of source Mo = 2.7 days

dN / dt = N₀ λ where dN / dt is initial activity , N₀ is initial number of atoms and λ is disintegration constant .

λ = .693 / half life

= .693 / 2.7

= .257

dN / dt = N₀ λ

20k = N₀ x .257

N₀ = 20 k /.257

= 20 k /.257  x

= 20k x .64383

dN / dt = N λ

dN / dt = 20k x .64383  x .257

= 3.3 GBq.

explanation:

earth's surface is mainly heated by the absorption of infrared radiation from the sun.

evaporation occurs because molecules in liquid water are warmed ( usually by the sun) and vibrate quicker, becoming less dense and rise.

condensation occurs because molecules in water vapor are cooled and therefore vibrate more slowly thus becoming more dense and eventually fall to earth.

lines of equal barometric pressure on a weather map are called: isobars : lines of equal temp on a weather map are called: isotherms.​

the current is 0.6

voltage ÷ resistance = current

so 12 ÷ 20 = 0.6