The half-life of a positron is very short. It reacts with an electron, and the masses of both are converted to two gamma-ray photons. e+10 +0−1e⟶2???? This reaction is called an annihilation reaction. The mass of an electron or positron is 9.109×10−31 kg. (a) Calculate the energy produced by the reaction between one electron and one positron. (b) Assuming that the two γ-ray photons have the same frequency, calculate this frequency. J ????photon= Hz

Respuesta :

Explanation:

(a)   It is known that relation between energy and mass is as follows.

            [tex]E = 2 \times mc^{2}[/tex]

where,    E = energy

              m = mass

              c = speed of light = [tex]3 \times 10^{8}[/tex] m/s

As it is given that mass is [tex]9.109 \times 10^{-31}[/tex] kg. So, putting the given values into the above formula as follows.

             [tex]E = 2 \times mc^{2}[/tex]

                       = [tex]2 \times 9.109 \times 10^{-31} kg \times 3 \times 10^{8}m/s[/tex]

                       = [tex]1.638 \times 10^{-13} J[/tex]

Therefore, we can conclude that the energy produced by the reaction between one electron and one positron is [tex]1.638 \times 10^{-13} J[/tex].

(b) When gamma ray photons are produced then they will have the same frequency. Relation between energy and frequency is as follows.

                    E = [tex]h \times \nu[/tex]   ..... (1)

where,     h = plank's constant = [tex]6.626 \times 10^{-34} J.s[/tex]

              [tex]\nu[/tex] = frequency

Also,     [tex]E = 2 \times mc^{2}[/tex] ........ (2)

Hence, equating equations (1) and (2) as follows.

                    [tex]h \times \nu[/tex] = [tex]2 \times mc^{2}[/tex]        

So,    

[tex]6.626 \times 10^{-34} Js \times \nu[/tex] = [tex]1.638 \times 10^{-13} J[/tex]

                           [tex]\nu[/tex] = [tex]1.236 \times 10^{20} Hz[/tex]

Thus, we can conclude that the frequency is [tex]1.236 \times 10^{20} Hz[/tex].

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