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Ch 39: Wave Functions and Uncertainty
Knight Calc - Physics for Scientists and Engineers 5th Edition
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796당신이 사용하는 게 아니라요?교과서 변경
39장, 문제 30c

An experiment finds electrons to be uniformly distributed over the interval 0 cm ≤ x ≤ 2 cm, with no electrons falling outside this interval. If 106 electrons are detected, how many will be detected in the interval 0.79 to 0.81 cm?

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Step 1: Understand the problem. The electrons are uniformly distributed over the interval 0 cm ≤ x ≤ 2 cm, meaning the probability density function is constant across this interval. The total number of electrons detected is 10^6, and we need to calculate how many electrons are detected in the subinterval 0.79 cm to 0.81 cm.
Step 2: Calculate the probability density. Since the distribution is uniform, the probability density function (PDF) is given by dividing the total number of electrons by the length of the interval. The length of the interval is 2 cm - 0 cm = 2 cm. Therefore, the PDF is \( \frac{10^6}{2} \) electrons per cm.
Step 3: Determine the length of the subinterval. The subinterval is from 0.79 cm to 0.81 cm, so its length is \( 0.81 - 0.79 = 0.02 \) cm.
Step 4: Calculate the number of electrons in the subinterval. Multiply the probability density by the length of the subinterval: \( \text{Number of electrons} = \text{PDF} \times \text{Length of subinterval} = \frac{10^6}{2} \times 0.02 \).
Step 5: Simplify the expression to find the number of electrons in the subinterval. This step involves performing the multiplication, but the final numerical result is not calculated here as per the instructions.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Uniform Distribution

Uniform distribution refers to a probability distribution where all outcomes are equally likely. In this context, the electrons are uniformly distributed over the specified interval, meaning that the probability of finding an electron in any sub-interval is proportional to the length of that sub-interval relative to the total length of the interval.
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가이드 코스
04:03
Probability Distribution Graph

Probability Density

Probability density describes how probability is distributed over a continuous range of values. For uniformly distributed electrons, the probability density can be calculated by dividing the total number of electrons by the length of the interval. This density allows us to determine the expected number of electrons in any smaller interval within the larger range.
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가이드 코스
8:13
Intro to Density

Calculating Expected Counts

To find the expected number of electrons in a specific interval, we multiply the probability density by the length of that interval. In this case, the length of the interval from 0.79 cm to 0.81 cm is 0.02 cm. By applying the uniform distribution principles, we can calculate how many of the total 10^6 electrons are likely to be found in this small segment.
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가이드 코스
04:44
Counting Significant Figures
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