Particle accelerators and high-energy beams

Overview

Recall questions on why probing small structures needs high energy, how a linear accelerator works and why its voltage alternates, magnets and vacuum in a ring, and creating new particles.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   Why must particles be given very high energies in order to probe small structures?

   Model answer

   The de Broglie wavelength of a particle is h/p, so only a large momentum gives a wavelength small enough to resolve detail on the scale of a nucleus or smaller.

2. 2

   Calculate the de Broglie wavelength of a particle whose momentum is 1.0 × 10⁻²¹ N s.

   Model answer

   λ = h/p = 6.63 × 10⁻³⁴ ÷ 1.0 × 10⁻²¹ = 6.6 × 10⁻¹³ m.

3. 3

   Describe how a linear accelerator increases the energy of a charged particle.

   Model answer

   The particle passes through a line of hollow electrodes and is accelerated across each gap by a potential difference, gaining energy qV at every gap so that its energy builds up along the line.

4. 4

   Why must the accelerating voltage in a linear accelerator alternate?

   Model answer

   The particle must always meet a field pointing the right way to speed it up, so the voltage on the electrodes has to reverse in step with the particle's arrival at each gap.

5. 5

   What is the role of magnetic fields in a ring accelerator?

   Model answer

   Magnetic fields provide the centripetal force through F = qvB that bends the beam round the ring, and further magnets focus the beam so it stays narrow.

6. 6

   Calculate the energy in joules gained by a proton accelerated through a potential difference of 2.0 × 10⁶ V.

   Model answer

   The energy gained is qV = 1.60 × 10⁻¹⁹ × 2.0 × 10⁶ = 3.2 × 10⁻¹³ J, which is 2.0 MeV.

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.