Chapter 25, Problem 72SCQ

(a)

Interpretation Introduction

Interpretation:

Energy evolved from the annihilation of an electron and a positron should be calculated.

Concept introduction:

Mass defect can be calculated using following formula,

${\text{Δm = m}}_{\text{R}}{\text{- m}}_{\text{p}}$

Here

$\text{Δm}$ is mass defect for the process

${\text{m}}_{\text{R}}$ is mass for the reactants

${\text{m}}_{\text{p}}$ is mass of the products

Conversion of amu to kJ

  $1amu=931.5MeV\times \frac{\left(1.602\times {10}^{-10}k\text{J}\right)}{1MeV}$

(b)

Interpretation Introduction

Interpretation:

Frequency of the gamma rays should be calculated using Planck’s equation.

Concept introduction:

Planck’s equation is given as:

    $\begin{array}{c}\text{E}\text{=}\text{hν}\\ \text{where, ν}=\text{frequency}\\ \text{h}\text{=}\text{Planck’s}\text{constant}\end{array}$

The energy increases as the wavelength of the light decreases.