What is probability per unit time

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SUMMARY

The discussion centers on the concept of probability per unit time as described in Ashcroft and Mermin's work. The probability that an electron experiences a collision in an infinitesimal time interval, dt, is defined as dt/τ, where τ represents the average time between collisions. While dt approaching zero results in a small probability, setting dt equal to τ yields a probability of 1. However, τ being an average indicates that collisions can occur both before and after this time, leading to confusion regarding the interpretation of these probabilities, particularly the probability of no collision, which is expressed as e-t/τ.

PREREQUISITES
  • Understanding of basic probability theory
  • Familiarity with the concept of average time (τ) in statistical mechanics
  • Knowledge of exponential functions and their applications in probability
  • Basic principles of quantum mechanics related to electron behavior
NEXT STEPS
  • Research the derivation of the equation for the probability of no collision, e-t/τ.
  • Study the concept of mean free path in kinetic theory of gases.
  • Explore the relationship between collision probability and half-life in quantum mechanics.
  • Examine the statistical interpretation of averages in physical systems.
USEFUL FOR

Students of physics, particularly those studying quantum mechanics, as well as researchers and educators seeking to clarify concepts related to collision probabilities and statistical mechanics.

mcodesmart
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I am reading Aschroft and Mermin and I came across the probability per unit time

I have trouble understanding the concept as it is. But they do try to explain.

They say that the probability that an electron will experience a collision in an ifinetismal time, dt, is just dt/τ.

From this i gather, that if the time dt is close to 0, the probabitly will be small. If the time dt is equal to τ, then the probability that an electron will collide is 1.

But in the next sentence, they say that τ is an average time that a collision will occur, meaning that the probability that it will occur at time τ cannot be 1, because if it is an average time, then, collision will occur sometimes longer that τ and sometimes shorter that time τ. All this has got me confused and I need some clarification.
 
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hi mcodesmart! :smile:
mcodesmart said:
They say that the probability that an electron will experience a collision in an ifinetismal time, dt, is just dt/τ.

From this i gather, that if the time dt is close to 0, the probabitly will be small. If the time dt is equal to τ, then the probability that an electron will collide is 1 …

this is like half-life

the probability of no collision after time t will be e-t/τ :wink:
 
I see.. it is not the probability of collision but the probability of NO collision..

Can you please explain how you get that from the statement that I provided in the OP..
 
(just got up :zzz:)
mcodesmart said:
I see.. it is not the probability of collision but the probability of NO collision..

Can you please explain how you get that from the statement that I provided in the OP..

oh come on

you do a bit of research and calculation, and see if you can get that equation! :wink:
 
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