Radioactivity.


by hhhmortal
Tags: radioactivity
hhhmortal
hhhmortal is offline
#1
May14-09, 11:35 AM
P: 176
1. The problem statement, all variables and given/known data

Three proton decays per cubic kilometer of water per year are detected by an array of photomultipliers immersed in the sea. Find the mean lifetime of the proton.


2. Relevant equations

t = 1 / lambda

3. The attempt at a solution

How is it possible to work this out without knowing the halflife?
Phys.Org News Partner Science news on Phys.org
Internet co-creator Cerf debunks 'myth' that US runs it
Astronomical forensics uncover planetary disks in Hubble archive
Solar-powered two-seat Sunseeker airplane has progress report
mgb_phys
mgb_phys is offline
#2
May14-09, 11:39 AM
Sci Advisor
HW Helper
P: 8,961
How many protons are there in a km^3 of sea water
How many decay per year?
So whats the decay rate?
hhhmortal
hhhmortal is offline
#3
May14-09, 02:06 PM
P: 176
Quote Quote by mgb_phys View Post
How many protons are there in a km^3 of sea water
How many decay per year?
So whats the decay rate?
Well I calculated the amount of protons per km^3 using moles and grams and it is
about 6 x 10^29 , but im not too sure if this is correct.

the decay rate is 3 proton per km^3 per year but what equation do I need to work out the mean halflife?

is it decay rate = (lambda)(N)e^-(lambda)(t) ?

mgb_phys
mgb_phys is offline
#4
May14-09, 03:39 PM
Sci Advisor
HW Helper
P: 8,961

Radioactivity.


It doesn't ask for a halflife it asks for an average lifetime.
If 3 in 6 x 10^29 decay per year - then the average time for a proton to decay is just 1/decay rate (from dimensions)
hhhmortal
hhhmortal is offline
#5
May14-09, 06:29 PM
P: 176
Quote Quote by mgb_phys View Post
It doesn't ask for a halflife it asks for an average lifetime.
If 3 in 6 x 10^29 decay per year - then the average time for a proton to decay is just 1/decay rate (from dimensions)
It makes sense now, thanks! I calculated the mean lifetime to be 2 x 10^29 years, which looks about right.


Register to reply

Related Discussions
Radioactivity Help! Advanced Physics Homework 3
Radioactivity Introductory Physics Homework 8
forces are actually involved in radioactivity High Energy, Nuclear, Particle Physics 23
radioactivity Introductory Physics Homework 1