Antiparticles, pair production & annihilation

Electrons in a fluorescent tube are accelerated from rest by a potential difference of 130 V.

Calculate the maximum speed of an electron that is accelerated from rest by this potential difference.

Explain why the average speed of the electrons in the tube is much less than the maximum speed you calculated in Question 08.1.

Scientists want to replace the mercury in fluorescent tubes with substance X.

Figure 12 is an emission spectrum for X.

White light consists of the whole range of visible wavelengths from 380 nm to 700 nm

Explain, with reference to Figure 12, whether white light can be produced by a fluorescent tube that uses X.

Figure 12 shows a maximum intensity peak that occurs at wavelength λ_peak.

Calculate, in eV, the energy change of an atom that produces a photon with a

A positive pion collides with a neutron and the following interaction is observed:

Σ⁰ is a neutral sigma particle with a strangeness of −1

The interaction can be used to deduce the classifications of the Σ⁰.

Identify the classifications of each particle in Table 1. Tick (✓) the appropriate boxes for each particle.

A conservation rule predicts that the following interaction cannot occur:

State the conservation rule. Go on to explain your answer.

One way in which neutral pions decay is

Compare the rest energies of the particles involved in this decay.

The decay of the neutral pion leads to the production of further gamma photons.

Explain why.

The Standard Model is a theory that classifies elementary particles. Evidence for the theory has been collected since about 1950. However, the term Standard Model has only been used since 1973.

Suggest why progress in particle physics is slow.

Monochromatic light is incident on a metal surface in a vacuum and photoelectrons are emitted from the surface. The photoelectric current I is the rate of flow of charge from the surface. The maximum kinetic energy of the photoelectrons is E_k(max).

The frequency of the light is then increased. There is no change to the rate at which energy is incident on the surface.

What happens to E_k(max) and I when the frequency is increased?

Three energy levels for an atom are shown.

Energy change E₁ leads to the emission of a photon of wavelength λ₁. Energy change E₂ leads to the emission of a photon of wavelength λ₂.

The neutral lambda particle Λ⁰ is a baryon with a strangeness of −1

One possible decay for a Λ⁰ is

Deduce the quark structure of a Λ⁰.

State and explain which interaction is involved in this decay.

An antiparticle of the neutral lambda particle decays into a neutral pion and particle X

Identify X.

The rest energy of a Λ⁰ is equal to the energy of a photon with a frequency

Determine, in MeV, the rest energy of a Λ⁰.

The discovery of particles such as the Λ⁰ is made by large international research teams.

Suggest one reason for this.

Carbon-14 d ys into nitrogen-14 with the release of a beta (β⁻) particle and an

State the change of quark character in β⁻ decay.

Figure 2 shows the distribution of kinetic energies of β⁻ particles from the decay of carbon-14.

Explain how Figure 2 supports the existence of the antineutrino.

The existence of the antineutrino was confirmed by experiments in which antineutrinos interact with protons. The equation for this interaction is:

Identify particle X.

The positron released in this interaction is annihilated when it encounters an electron. A pair of gamma photons is then produced. Particle X can be absorbed by a nucleus. This produces another gamma ray. Table 1 contains data for three gamma photons detected during an antineutrino–proton interaction experiment.

Deduce which of the three gamma photons could have been produced by positron annihilation.

The diagram shows the three lowest energy levels for an atom. The energy levels have been drawn to scale.

Transitions of electrons between these energy levels produce photons of the following frequencies:

What is the difference in energy between the ground state and energy level 1 ?

A light-emitting diode (LED) emits light over a narrow range of wavelengths.

Two LEDs L_G and L_R are adjusted to give the same maximum light intensity. L_G emits green light and L_R emits red light.

Figure 3 shows how the light output of the LEDs varies with the wavelength λ.

Figure 3

Light from L_R is incident normally on a plane diffraction grating.

Determine N, the number of lines per metre on the grating.

Suggest one possible disadvantage of using the fifth-order maximum to determine N

Figure 4 shows part of the current−voltage characteristics for L_R and L_G.

When the linear part of the characteristic is extrapolated, the point at which it meets the horizontal axis gives the activation voltage V_A for the LED.

Determine, using Figure 4, V_A for L_R.

It can be shown that:

where h = the Planck constant.

Deduce a value for the Planck constant based on the data given about the LEDs.

Figure 5 shows a circuit with L_R connected to a resistor of resistance R.

The power supply has emf 6.10 V and negligible internal resistance. The current in L_R must not exceed 21.0 mA.

Deduce the minimum value of R.

Determine whether the following reaction is a possible decay for the neutral pion π⁰.

State the two possible quark configurations of a π⁰.

^{0 0} A student suggests that the kaon K and the anti-kaon K are the same particle.

Discuss whether this suggestion is correct.

The nucleus is held together by a force. It was predicted that a particle exists that is responsible for this force. The particle itself must experience this force.

The particle would have a rest energy between that of an electron and half that of a nucleon.

Discuss whether a kaon, a muon and a pion each have the properties of the predicted particle.

Information about these three particles is in the Data and Formulae Booklet.

Which graph shows the variation of momentum p with wavelength λ of a photon?

A monochromatic light wave travels from glass into air.

Which row shows what happens to the wavelength, speed and photon energy?

A photon of ultraviolet radiation has a frequency of 1.5 × 10¹⁵ Hz.

What is the momentum of the photon?

Two gamma photons are produced when a muon and an antimuon annihilate each other.

What is the minimum frequency of the gamma radiation that could be produced?

The decay is represented by this equation:

Complete the equation to show the decay by filling in the gaps.

Explain which fundamental interaction is responsible for the decay in question 01.1.

One decay mechanism for the decay of results in the argon nucleus having an excess energy of 1.46 MeV. It loses this energy by emitting a single gamma photon.

Calculate the wavelength of the photon released by the argon nucleus.

The potassium isotope can also decay by a second decay process to form a

Suggest how the emissions from a nucleus of decaying potassium can be used to confirm which decay process is occurring.

the same.

Which row in the table is correct?