An experiment has four possible outcomes, labeled A to D. The probability of A is PA = 40% and of B is PB = 30%. Outcome C is twice as probable as outcome D. What are the probabilities PC and PD?
Ch 39: Wave Functions and Uncertainty
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796Non è quello che usi tu?Cambia libro di testo
Capitolo 39, Problema 9
When 5×1012 photons pass through an experimental apparatus, 2.0×109 land in a 0.10-mm-wide strip. What is the probability density at this point?
Guida verificata passo dopo passo1
Step 1: Understand the problem. The probability density is defined as the probability per unit area. To calculate it, we need to determine the fraction of photons that land in the specified strip and divide it by the area of the strip.
Step 2: Calculate the fraction of photons that land in the strip. This is given by the ratio of the number of photons landing in the strip to the total number of photons: \( \text{Fraction} = \frac{2.0 \times 10^9}{5.0 \times 10^{12}} \).
Step 3: Determine the area of the strip. The width of the strip is given as \( 0.10 \ \text{mm} \), which needs to be converted to meters: \( 0.10 \ \text{mm} = 0.10 \times 10^{-3} \ \text{m} \). Assume the length of the strip is \( 1 \ \text{m} \) (if not specified, this is a common assumption for such problems). Thus, the area is \( \text{Area} = \text{Width} \times \text{Length} = (0.10 \times 10^{-3}) \times 1 \).
Step 4: Calculate the probability density. The probability density is the fraction of photons divided by the area of the strip: \( \text{Probability Density} = \frac{\text{Fraction}}{\text{Area}} = \frac{\frac{2.0 \times 10^9}{5.0 \times 10^{12}}}{(0.10 \times 10^{-3}) \times 1} \).
Step 5: Simplify the expression to find the probability density. Perform the division and simplify the units to express the final result in terms of \( \text{m}^{-2} \).

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Concetti chiave
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Photon
A photon is a quantum of electromagnetic radiation, representing the smallest discrete amount of light or other electromagnetic energy. Photons are massless particles that travel at the speed of light and exhibit both wave-like and particle-like properties. Understanding photons is essential for analyzing interactions in experiments involving light and energy transfer.
Probability Density
Probability density refers to the likelihood of finding a particle, such as a photon, in a specific region of space per unit area. It is calculated by dividing the number of particles that land in a given area by the area itself. In this context, it helps quantify how concentrated the photons are in the specified strip, providing insight into their distribution.
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Intro to Density
Area Calculation
Area calculation is fundamental in physics for determining the spatial extent of a region where events occur, such as the landing of photons. In this scenario, the width of the strip (0.10 mm) must be converted to appropriate units (e.g., square meters) to calculate the probability density accurately. This concept is crucial for relating the number of photons to the area they occupy.
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Calculating Work As Area Under F-x Graphs
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