Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 38: Problem 4

Beta decay by positron emission is soon followed by a pair of 511 -keV gamma rays. Why?

Short Answer

Expert verified
After beta decay by positron emission occurs, the positron emitted comes into contact with an electron, leading to their annihilation. This matter-to-energy conversion results in the emission of two gamma rays, each carrying energy of 511 keV due to the mass-energy equivalence (E=mc^2 where m is the mass of an electron or positron), hence why beta decay is soon followed by the emission of a pair of 511-keV gamma rays.

Step by step solution

01

Understanding Beta decay by positron emission

In beta decay by positron emission, a proton within the nucleus of a radioactive atom is transformed into a neutron. This process also results in the creation and emission of an anti-neutrino and a positron. The positron is a subatomic particle which is the antiparticle of the electron, having the same mass but an opposite charge.
02

Describing the movement of the emitted positron

After the positron has been emitted, it starts travelling away from the nucleus. However, since it is surrounded by electrons (which are fundamentally opposite in nature), it doesn't travel far before it comes into contact with an electron.
03

Explaining the reason for gamma rays

When the positron comes into close proximity with an electron, annihilation occurs. This is when a particle and its antiparticle meet and destroy each other. The mass of both particles is effectively converted into energy, which is then released as two high-energy gamma rays. These gamma rays, each carrying an energy of 511-keV (because 511 keV/c^2 is approximately the mass of an electron or positron), are then emitted in nearly opposite directions, preserving linear momentum.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Write the symbol for the germanium isotope with 44 neutrons.

Nitrogen- 13 is a 10 -min-half-life isotope used to "tag" ammonia for PET scans, including quantification of myocardial infarction. Consider an intravenous injection incorporating \(20 \mathrm{mCi}\) of \(\mathrm{N}-13\) Plot a graph of \(\mathrm{N}-13\) activity versus time, with your vertical axis logarithmic and your horizontal axis linear. Why is the graph a straight line? What's the significance of its slope?

Show that the decay constant and half-life are related by \(t_{1 / 2}=\ln 2 / \lambda \simeq 0.693 / \lambda.\)

In the dangerous situation of prompt criticality in a fission reactor, the generation time drops to \(100 \mu\) s as prompt neutrons alone sustain the chain reaction. If a reactor goes prompt critical with \(k=1.001,\) how long does it take for a 100 -fold increase in reactor power?

Why are fission fragments necessarily radioactive?
See all solutions

Recommended explanations on Physics Textbooks

Atoms and Radioactivity

Read Explanation

Energy Physics

Read Explanation

Fluids

Read Explanation

Kinematics Physics

Read Explanation

Mechanics and Materials

Read Explanation

Electrostatics

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free