Uranium -238 has a half life of 4.5 billion years. How long will it take a 2g sample of U-238 to contain just 0.4g of U-238?
Radioactive decay is a process where the nucleus of an unstable atom, such as Uranium-238 loses energy by emitting radiation.
The half life is the average time it take for half the nuclei in a sample to undergo radioactive decay.
Given an initial sample of x with mass N(0). After a time t the mass of x left in the sample N(t) is given by:
N(t) = N(0).2-t/t1/2 (1)
Where t1/2 is the halflife.
To answer the question we need to find t. Rearranging equation (1) we have:
- t1/2 log2[N(t)/N(0)] = t (2)
subbing the values from the question into (2)
-4.5x109 log2 [0.4/ 2] = 10.4 billion years
RE
Related Physics A Level answers
All answers ▸A diver of mass 60kg stands on the end of a diving board (2m in length). Calculate the upward force exerted on the retaining spring which is 30cm from the start of the diving board.
A box initially at rest is on a plank, of length 5m, that is elevated at an angle such that tan(a)=3/4. When it reaches the end of the plank it has velocity 5ms^-1. Calculate the average frictional force on the box.
Why does a single slit diffraction pattern occur?
Describe energy transformations in a oscillating pendulum, which undergoes simple harmonic motion. How this implies the velocity at critical (lowest and highest) points?