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Contests/Gnit Weekly Challenge Standard 002 (GWCS002)/Problem 6 Compton effect and momentum of recoil electrons
Problem 6

Compton effect and momentum of recoil electrons

Finished
490 ptsLv.8 IntermediateQuantum
2026/07/22 21:00〜2026/07/22 21:45
Author: admin02

Problem Statement

When an X-ray photon with wavelength λ\lambdaλ collides with a stationary free electron of mass mmm, the X-ray photon is scattered at an angle θ\thetaθ relative to its original direction of propagation, and its wavelength changes to λ′\lambda'λ′. This phenomenon is called the Compton effect.

The wavelength λ′\lambda'λ′ of the scattered X-ray photon satisfies the following relationship, using Planck's constant hhh and the speed of light in a vacuum ccc:

λ′−λ=hmc(1−cos⁡θ)\lambda' - \lambda = \frac{h}{mc}(1 - \cos\theta) λ′−λ=mch​(1−cosθ)

During the collision, the electron receives energy and momentum from the X-ray photon and is ejected as a recoil electron. By considering the conservation of momentum for the entire system before and after a collision, if we know the wavelength of the scattered X-ray photon λ′\lambda'λ′, the wavelength of the X-ray photon before the collision λ\lambdaλ, and the scattering angle θ\thetaθ, we can directly determine the magnitude of the momentum of the ejected recoil electron pep_epe​.

Now, when an X-ray photon with wavelength λ\lambdaλ collides with a stationary electron, the wavelength of the X-ray photon scattered in the direction of scattering angle θ=90°\theta = 90°θ=90° is 101100\frac{10¹}{100}100101​ times the original wavelength. In this collision, express the magnitude of the momentum of the ejected recoil electron pep_epe​ using the magnitude of the momentum of the X-ray photon before the collision ppp.

Constraints

  • m=9.1×10−31 kgm = 9.1 \times 10^{-31} \ \text{kg}m=9.1×10−31 kg
  • c=3.0×108 m/sc = 3.0 \times 10^8 \ \text{m/s}c=3.0×108 m/s
  • h=6.6×10−34 J⋅sh = 6.6 \times 10^{-34} \ \text{J}\cdot\text{s}h=6.6×10−34 J⋅s

Input Format

When the dimensionless ratio pep\frac{p_e}{p}ppe​​ of the momentum of the recoiling electron pep_epe​ and the momentum of the X-ray photon before collision ppp is found, this value can be expressed as N101\frac{\sqrt{N}}{10¹}101N​​. Enter the value of the natural number NNN inside the square root.

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