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A gamma-ray photon changes into a proton-antiproton pair. Ignoring momentum conservation, what must have been the wavelength of the photon (a) if the pair is stationary after creation, and (b) if each moves off at 0.6c, perpendicular to the motion of the photon? (c) Assume that these interactions occur as the photon encounters a lead plate and that a lead nucleus participates in momentum conservation. In each case, what fraction of the photon's energy must be absorbed by a lead nucleus?

Short Answer

Expert verified

(a) The wavelength of the photon if the pair is stationary after creation is6.61×10-16 m.

(b) The wavelength of the photon if the pair is stationary after creation is5.29×10-16 m.

(c) The fraction of the photon energy must be absorbed by a lead nucleus in each case 0.00483are and 0.00627respectively.

Step by step solution

01

Significance of the wavelength

The wavelength is described as the distance over the shape of a particular wave repeats. However, wavelength is described as the distance amongst the identical points of a waveform.

02

(a) Determination of the wavelength if the pair is stationary

If the pair remains stationary, then the total amount of energy is in the form of the internal energy. Then the equation of the energy of the antiproton and the proton is expressed as:

hcλ=2mpc2λ=hc2mpc2∣λ=h2mpC

Here, λis the wavelength, his the Planck’s constant, cis the velocity of the light and mpis the mass of the proton.

Substitute 6.626×10-34J·sforh,1.67×10-27kgformpand3×108m/sfor cin the above equation.

λ=6.626×10-34J·s21.67×10-27kg3×108m/s=6.626×10-34J·s25.01×10-19kg·m/s=6.626×10-34J·s1.002×10-18kg·m/s=6.61×10-16J·s2/kg·m

Hence, further as.

λ=6.61×10-16J·s2/kg·m×kg·m2/s21J=6.61×10-16kg·m2s2/kg·m·s2=6.61×10-16m

Thus, the wavelength of the photon if the pair is stationary after creation is=6.61×10-16m .

03

(b) Determination of the wavelength if the movement is perpendicular to the motion of the photon

The equation of the wavelength of the proton is expressed as:

hcλ=2γ0.6cmpc2λ=hc2γ0.6cmpc2λ=hc2γ0.6cmpc

Here, λis the wavelength, his the Planck’s constant, localid="1658241714488" cis the velocity of the light,γ0.6cis the velocity of the pair and localid="1657595455489" mpis the mass of the proton.

Substitutelocalid="1657592042370" 6.626×10-34J·sforh,1.67×10-27kgformp,1.25forγ0.8cand3×108m/sin forcthe above equation.

localid="1657592117578" λ=6.626×10-34J·s2(1.25)1.67×10-27kg3×108m/s=6.626×10-34J·s2.55.01×10-19kg·m/s=6.626×10-34J·s1.2525×10-18kg·m/s=5.29×10-16J·s2/kg·m

Hence, further as.

λ=5.29×10-16J·s2/kg·m×kg·m2/s21J=5.29×10-16kg·m2s2/kg·m·s2=5.29×10-16m

Thus, the wavelength of the photon if the pair is stationary after creation is =5.29×10-16

04

(c) Determination of the fraction of the photon’s energy in the first case

The equation of the velocity of the photon and the lead plate is expressed as:

hλ=mpbupbupb=hmpbλ

Here, upbis the velocity of the photon and the lead plate, λis the wavelength in the first case, localid="1657593020754" mpbis the Planck’s constant and is the mass of the combined proton and the lead nucleus.

Substitute localid="1657593961895" 6.626×10-34kg·m2/sforh,207.2u×1.67×10-27kg/uformpband6.61×10-16mfor λin the above equation.

upb=6.626×10-34kg·m2/s207.2u×1.67×10-27kg/u6.61×10-16m=6.626×10-34kg·m2/s2.28×10-40kg·m=2.9×106

The equation of the energy of the proton is expressed as:

Ep=hcλ

Here, Epis the energy of the proton, his the Planck’s constant and cis the velocity of the light.

Substitute the values in the above equation.

Ep=6.626×10-34kg·m2/s3×108m/s6.61×10-16m=1.98×10-25kg·m3/s26.61×10-16m=3.007×10-10kg·m2/s2

The equation of the fraction of the photon’s energy in the first case is expressed as:

E=12mpbupb2Ep∣

Here, Epis the energy of the proton, upbis the velocity of the photon and the lead plate andmpbis the mass of the combined proton and the lead nucleus.

Substitute the values in the above equation.

E=12207.2u×1.67×10-27kg/u2.9×106m/s23.007×10-10kg·m2/s2=123.46×10-25kg8.41×1012m2/s23.007×10-10kg·m2/s2=1.45×10-12kg·m2/s23.007×10-10kg·m2/s2=0.00483

05

(c) Determination of the fraction of the photon’s energy in the second case

The equation of the velocity of the photon and the lead plate is expressed as:

hλ=mpbupbupb=hmpbλ

Here, upbis the velocity of the photon and the lead plate, λis the wavelength in the second case, his the Planck’s constant and localid="1657594958229" mpbis the mass of the combined proton and the lead nucleus.

Substitute 6.626×10-34kg·m2/sforh,207.2u×1.67×10-27kg/uformpband

5.28×10-16 mfor λin the above equation.

upb=6.626×10-34kg·m2/s207.2u×1.67×10-27kg/u5.28×10-16m=6.626×10-34kg·m2/s1.82×10-40kg·m=3.7×106m/s

The equation of the energy of the proton is expressed as:

Ep=hCλ∣

Here, Epis the energy of the proton, his the Planck’s constant and cis the velocity of the light.

Substitute the values in the above equation.

Ep=6.626×10-34kg·m2/s3×108m/s5.28×10-18m=1.98×10-25kg·m3/s25.28×10-18m=3.75×10-10kg·m2/s2

The equation of the fraction of the photon’s energy in the second case is expressed as:

E=12mpbupb2Ep

Here, Epis the energy of the proton,upbis the velocity of the photon and the lead plate and mpbis the mass of the combined proton and the lead nucleus.

Substitute the values in the above equation.

E=12207.2u×1.67×10-27kg/u3.7×106m/s23.75×10-10kg·m2/s2=123.46×10-25kg1.369×1013m2/s23.75×10-10kg·m2/s2=2.36×10-12kg·m2/s23.75×10-10kg·m2/s2=0.00627

Thus, the fraction of the photon energy must be absorbed by a lead nucleus in each case are0.00483 and0.00627 respectively.

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