Recent content by huyen_vyvy

I was looking at the beta decay process of 22Na and I have a question that really bugs me. 22Na spin +3 decays into 21Ne in the excited state with spin 2, and then this Ne nucleus will emit one photon and jumps down to the ground state with spin 0. if only one photon is emitted, isn't...

try reading "The Feynman lectures on physics Volume III" he gives a very good explanation of the interferometer. Basically you put a light source behind the 2 slits and between them, when an electron goes through a slit, it will trigger the light source to emit a photon, and depending on the...

What is really meant by temperature and negative absolute temperature? Is that an abnormal state that happens during population inversion in laser?

just wondering why all photons produced in a laser beam are coherent? what forces them to have the same phase?

in the photon's ref frame, it takes zero time to travel across any distance. so things still make sense?

in your reference frame, no. Time ticks slower in your ref frame, t= 10years/ sqrt(1-v2/c2) for the original question, I think if a person was to travel at the speed of light, then it's impossible that "after 1 second" makes sense in that ref frame. I mean, in his ref frame, NO TIME has passed...

binomial expansion is the easiest way to answer this question though, (1+x)^k=1+kx+k(k-1)/2*x^2+... and we can ignore those higher degrees of x.

Have a look at Victor Stenger's book called "God: the failed hypothesis", in which he argues that although at the big bang, the universe had maximum entropy, the universe has ever since expanded so it has more space to "throw" its entropy.

honestly, this problem can be made very easy like this: volume= 1/3height * area of base. Height is z=3, area of base is the area of a right triangle with two sides being 1 and 2. Therefore, V=1.

I read from Victor Stenger's books that maximum entropy exists in black holes or singularities. So, at the Big bang, the universe had its maximum entropy. Does it mean that entropy has DECREASED since then? Stenger explained that since the universe expands, it has more space for entropy...

I know this is cheating but I found the answer here http://physuna.phs.uc.edu/suranyi/Modern_physics/Lecture_Notes/modern_physics6.html

I guess that you have to estimate the probability for EACH single atom to tunnel through the potential barrier and then multiply all the probabilities together and get something like almost 0. However, I don't know how to calculate the energy for each atom and how many atoms our body has.

oops my bad, i didn't read the question carefully enough.

M2= 5*m1 => A2 =10^5*a1

can you explain what q, k, x, y and L are? I kinda can't follow what you were doing up there.