Particles

Explain how the pattern produced on the screen supports the idea that the electron beam is behaving as a wave rather than as a stream of particles.

Particle behaviour would only produce a patch/circle of light /small spot of light or Particles would scatter randomly
Wave property shown by diffraction/ interference
Graphite causes (electron)waves/beam to spread out /electrons to travel in particular directions
Bright rings/maximum intensity occurs where waves interfere constructively/ are in phase
for a diffraction grating maxima when n lambda = d sin theta

Describe the nature of the forces that act between nucleons and how these forces can maintain nuclear stability.

In your answer, describe:

• the forces of repulsion and attraction that act between nucleons

• exchange particles associated with these forces

• the role of these forces in keeping the nucleus stable.

Forces of repulsion and attraction that act between nucleons:

• (Repulsion =) Electromagnetic (between protons)

• (Attraction=) Gravitational force (between nucleons) or idea that gravitational is negligible

• (Both repulsive and attractive =) Strong interaction

Exchange particles associated with these forces:

• The pion is the strong interaction's exchange particle. • Virtual photons for electromagnetic

• Treat mention of graviton for gravity as neutral Role of these forces in keeping nucleus stable:

• Idea that strong interaction is greater in magnitude than any of the other interactions/ idea SI dominates.

• Strong interaction has short-range attraction acting on neighbouring nucleons (up to 3 to 4 fm).

• Strong interaction has very short-range repulsion at distances less than approximately 0.5 fm.

• Strong interaction acts between nucleons.

What property defines a hadron?

particles that experience the strong (nuclear) force/interaction

What is the quark structure of a baryon?

particles composed of three quarks

What is the quark structure of a meson?

particles composed of a quark and an antiquark

State what interaction is responsible for this decay when strangeness is involved.

weak interaction
strange not conserved or there is a change/decay of quark (flavour)

What is meant by an excited atom?

an electron/atom is at a higher level than the ground state

Describe the process by which mercury atoms become excited in a fluorescent tube.

• electrons (or electric current) flow through the tube

• and collide with orbiting/atomic electrons or mercury atoms

• raising the electrons to a higher level (in the mercury atoms)

What is the purpose of the coating on the inside surface of the glass in a fluorescent tube?

• photons emitted from mercury atoms are in the ultra violet (spectrum) or high energy photons

• max 3 these photons are absorbed by the powder or powder changes frequency/wavelength

• and the powder emits photons in the visible spectrum

• incident photons have a variety of different wavelengths

State and explain which conservation law may be used to show that it is an anti-neutrino rather than a neutrino that is released in beta decay.

lepton number must be conserved
lepton number before decay equals zero hence after decay lepton number of electrons cancels with lepton

What must be done to validate the predictions of an unconfirmed scientific theory?

hypothesis needs to be tested by experiment
experiment must be repeatable

State what is meant by the threshold frequency of the incident light.

below a certain frequency (called the threshold frequency) no electrons emitted
or minimum frequency for electrons to overcome work function

Explain why the photoelectric effect is not observed below the threshold frequency.

(light travels as photons) energy of a photon depends on frequency
below threshold frequency (photon) does not have enough energy to liberate an electron