Recent Developments in Physics - Study Notes

Chapter Summary

This last unit shows where the physics you have learnt is being used today. It starts with nanoscience: at the nanoscale, quantum confinement and the large ratio of surface area to volume make materials behave differently from the same material in bulk. It then introduces robotics, which combines engineering and science, and the use of artificial intelligence in robots. After that comes physics in medicine, from X-rays to MRI. The unit ends with particle physics and cosmology, including the discovery of the Higgs boson and the detection of gravitational waves.

Learning Objectives

• Define nanoscience and nanotechnology and give examples of their applications.
• Distinguish between the top-down and bottom-up methods of making nanomaterials.
• List the main components of a robot and the different types of robots.
• State what artificial intelligence aims to do in robotics.
• Describe how inventions in physics led to medical diagnostic and treatment tools.
• Explain basic ideas in particle physics and cosmology.

Key Concepts and Definitions

• Nanometer: A unit of length equal to one-billionth of a metre (\(10^{-9}\) m).
• Top-down Approach: Bulk material is broken down to nanometre size by mechanical or chemical processes.
• Bottom-up Approach: Nanomaterials are built up by arranging individual atoms or molecules.
• Actuators: The parts of a robot that convert energy into movement, either linear or rotational.
• Holography: A method of recording and reproducing three-dimensional images. A laser beam is split into two parts; the light scattered from the object interferes with the reference beam and the interference pattern is recorded as the hologram. Polaroids are not what makes a hologram; they are used in polarised-glasses 3D viewing.
• Qubits: The basic unit of information in a quantum computer. A qubit can be 0, 1, or a superposition of both at the same time.

Worked Methods

Classification of Solids by Size

Solids are grouped by particle size. If a particle is smaller than 100 nm, the solid is called a nano solid. If it is larger than 100 nm, it is a bulk solid. Gold is a good example: bulk gold is yellow, but gold nanoparticles can look red, because optical, chemical and physical properties change at the nanoscale.

Medical Diagnosis through Physics

Many imaging methods in hospitals come straight from physics. MRI is based on Nuclear Magnetic Resonance (NMR). Hydrogen nuclei in the body are placed in a strong magnetic field and absorb radio waves at a resonance frequency. Differences in this signal between tissues are used to build images of internal organs and to locate tumours.

Common Exam Traps

• The word 'robot' comes from the Czech word robota, meaning forced labour. Do not confuse the origin of the word with the technical definition of a robot.
• The Higgs particle is not a nanomaterial. It is a subatomic particle linked to the field that gives other particles their mass.
• Gravitational waves do not travel slower than light. They travel at the speed of light.

Exam Tips

• Richard Feynman is credited with first suggesting the idea of nanotechnology, in his talk about arranging individual atoms.
• Aluminium is chosen for robot parts that need to be light and easy to work with; steel is chosen where strength is needed.
• Learn the six main types of industrial robots: Cartesian, SCARA, Cylindrical, Delta, Polar and Vertically articulated.
• Remember the dates: Einstein published general relativity in 1915 and predicted gravitational waves from it in 1916. LIGO detected them directly in September 2015, and the result was announced in 2016.