Skip to main content

Nitrogen-13 is used in tracers injected into the bloodstream for positron emission tomography (PET). The half-life...

Half-life is the time period in which a substance reduces to 50% of its original value. Thus, a substance reduces to 50% original value in 1 half-life, to 25% in 2 half-lives, 12.5% in 3 half-lives and so on. Here, nitrogen-13 has a half-life of 10 minutes. That means, 50% of nitrogen-13 decays in 10 minutes. 


The number of half-lives can be calculated by using the following expression:


2^n = 100 / (% of original...

Half-life is the time period in which a substance reduces to 50% of its original value. Thus, a substance reduces to 50% original value in 1 half-life, to 25% in 2 half-lives, 12.5% in 3 half-lives and so on. Here, nitrogen-13 has a half-life of 10 minutes. That means, 50% of nitrogen-13 decays in 10 minutes. 


The number of half-lives can be calculated by using the following expression:


2^n = 100 / (% of original content left)


where, n is the number of half-lives. Here, 17.8% of the original content is left. 


Therefore, 2^n = 100/17.8 


or n log 2 = log (100/17.8)


solving this equation, we get, n = 2.49


That is, in 2.49 half-lives, a substance will decay to 17.8% of its original content. 


Since the half-life of nitrogen-13 is 10 minutes, it will take 24.9 min (= 2 half lives x 10 min per half life) for it to decay to 17.8% of its original value.


Hope this helps. 

Comments

Post a Comment

Popular posts from this blog

What is the meaning of "juggling fiends" in Macbeth?

Macbeth is beginning to realize that the three witches have been deceiving him since he first encountered them. Like jugglers, they have kept changing their forecasts in order create confusion. This is particularly apparent when the Second Apparition they raise in Act IV,   Scene 1 tells him that no man of woman born can overcome him in hand-to-hand battle--and then Macbeth finds himself confronted by the one man he has been avoiding out of a... Macbeth is beginning to realize that the three witches have been deceiving him since he first encountered them. Like jugglers, they have kept changing their forecasts in order create confusion. This is particularly apparent when the Second Apparition they raise in Act IV,   Scene 1 tells him that no man of woman born can overcome him in hand-to-hand battle--and then Macbeth finds himself confronted by the one man he has been avoiding out of a sense of guilt, and that man tells him: Despair thy charm. And let the angel whom thou still hast serve...
Post a Comment
Read more

What are some external and internal conflicts that Montag has in Fahrenheit 451?

 Montag, the protagonist of Fahrenheit 451, faces both external and internal conflicts throughout the novel. Some examples of these conflicts are: External Conflicts: Conflict with the society: Montag lives in a society that prohibits books and critical thinking. He faces opposition from the government and the people who enforce this law. Montag struggles to come to terms with the fact that his society is based on censorship and control. Conflict with his wife: Montag's wife, Mildred, is completely absorbed in the shallow and meaningless entertainment provided by the government. Montag's growing dissatisfaction with his marriage adds to his external conflict. Conflict with the fire captain: Montag's superior, Captain Beatty, is the personification of the oppressive regime that Montag is fighting against. Montag's struggle against Beatty represents his external conflict with the government. Internal Conflicts: Conflict with his own beliefs: Montag, at the beginning of th...
Post a Comment
Read more

Discuss movements that were inspired by the Civil Rights Movement and list one success for each group.

African-Americans contributed in a very big way during World War II. These contributions were demonstrated at home and on the battlefield. After the war, African-Americans properly felt it was time for them to achieve equality with white Americans. During the 1950's, the modern Civil Rights Movement was born and it had a number of successes (integration of the military and Brown vs. Board of Education as examples.) This success inspired other activists to demand change... African-Americans contributed in a very big way during World War II. These contributions were demonstrated at home and on the battlefield. After the war, African-Americans properly felt it was time for them to achieve equality with white Americans. During the 1950's, the modern Civil Rights Movement was born and it had a number of successes (integration of the military and Brown vs. Board of Education as examples.) This success inspired other activists to demand change for their agendas. Two examples of moveme...
Post a Comment
Read more