Describe the interaction that would take place using terms f

Describe the interaction that would take place (using terms for the physical processes) if:

(a) An Xray and positron collided. Is the wave-like or particle-like nature dominant?

(b) A positron and silver pinball collided. Is the wave-like or particle-like nature dominant?

(c) An Xray and silver pinball collided. Is the wave-like or particle-like nature dominant?

NOTE: I\'m confused as how to answer this. For example in part a, I know that a positron is the anti-particle of an electron, so if it collided with Xrays, which are produced by electrons does this count as an electron-positron collision that results in annihilation? I think it might be more partlice-like in nature but I\'m not sure. For part b, if a positron and pinball collided would that result in some kind of scattering like Compton Scattering? And for part c, I\'m not sure where to start on how to answer it. I know Xrays can\'t travel through the silver, so would there be some kind of deflection and/or scattering as well?

Solution

Ans a: Understanding the interactions:

Step1 : The nature of x-ray at high energy

X ray is electromagnetic radiation of very short wavelength.It is produced by high energy electrons.

When X ray interacts with positron, it will be in high energy regime. So xray should be considered as

a photon.

Step 2: Interaction of x-ray photon with positron

Case A: Scattering

The reaction of photon with positron will be like a compton scattering if not absorbed.

The corresponding equation will be:

Positron + X-ray photon -----> Positron + Xray photon :

Case B Absorption

The photon can collide with positron, it may get absorbed. If the xray photon is absorbed,

the reaction will be

Positron + X-ray photon ---> high energy positron.

Ans B: Pinball-Positron Interaction

Step1: The nature of the positron & pinball in this interaction

A pinball is in low energy regime. The positron is an energetic particle. The nature of the interaction depends

on the momentum of the positron.

Step2 : The possible interaction

Case A: Bragg diffraction:

If the momentum(p) of the positron is such that the corresponding de-broglie

wavelength satisfies the condition:

n\\lambda = 2 d sin\\theta

where

\\lambda= h/ mv

then dirraction will take place.

Case B : If the momentum of the positron does not satisfy Bragg condition,

particle-particle collision will take place. During this collision two things can happen:

(i)The positron hits the ball, but does not hit an electron of the silver atom.

It will get scattered. As the size of positron and electron are both very small,

the probability of this interaction is very high.

(ii) If the positron hits an electron in the pin-ball. It annihilates and produce a photon.

Ans C:Xray & Pinball collides

Step 1: The nature of the interaction

This interaction happens in low energy regime. Xray can be represented as photons only in

high energy regime where quantum picture needs to be considered.

But in this regime, X ray will behave as waves.

So it will be a wave-crystal interaction.

Step2: The result

Diffraction will result in the process.

of KeV/ MeV range.

is produced