Perhaps due to a lack of details regarding his or their martyrdom, the Catholic Church pulled Saint Valentine from its liturgical veneration in 1969. Since that time, the holiday has expanded world-wide to areas that have never heard of early Roman martyrs. What a descent. From ecstatic religious devotion to a crude worshipping at the altars of sex and money. The now unholy day is coming up soon, and I thought that the following exchange would be appropriate for the occasion:
I am sorry for bothering you with this question.
But my high school students are asking this questions and I am not able to answer. Could you help me?
You wrote in Physics forum.
“When energy is released, it means that the binding is increased. The number of nucleons in gamma decay (emission of a photon, if I recall) stays constant. Therefore, the binding energy per nucleon increases.”
I am not able to find any textbooks or website explaining this. Could you indicate where I can find it so that I can explain iit.
No bother at all. It helps to remember things to be asked easy questions.
Any problems you have are likely a matter of the definition of the words. Try this wikipedia entry:
Thank you for your reply.
I have read your link.
The exam question is this.
A freshly-prepared sample of cobalt-64 decays by the emission of gamma-ray photons. The decay may be represented by the nuclear equation energy. (This should be Co to Co + energy )
After this decay, the binding energy per nucleon has
A. increased in magnitude because energy has been emitted from the nucleus.
B. decreased in magnitude because energy has been emitted from the nucleus.
C. stayed constant because the number of nucleons in the nucleus is unchanged.
D. stayed constant because the proton number is unchanged.
And the answer is A.
The question is that if energy is emitted, the total energy is lower. Then why the binding energy is increasing?
Thank you for your time.
I can’t explain it better than Wikipedia.
Oh, maybe I can. You are confused only because the sign seems that it should be wrong. Let me put it in human terms.
Think of binding energy as “love”. Particles stay together because they are in love. The amount of love is called the binding energy.
When a pair emits a gamma ray, that is like a problem that was hurting their relationship. It goes away. The result is that they fall deeper in love. Their binding energy increases.
Nothing could be more natural.
Here’s another way of looking at it. The way your intuition would prefer to take care of it, the binding energy should be negative because positive energy was taken away by the gamma ray. This makes complete sense, but so does the other way of looking at it.
You can either write down the answer that you think is correct (and have trouble talking with physicists) or you can agree that binding energy is a positive amount (that contributes negatively to the mass of the bound state as the Wikipedia article makes clear), but your instructor will mark your test wrong. Later, when you write a text book, you can correct this error. But for now, try to not be a nail that sticks up too much.
Thank you very much.
I will contemplate on it.