Recent Developments in Physics: One Mark Questions, Book Back Answers and Notes

About Recent Developments in Physics

Hard ~120 min study

Unit 11 is different from the rest of the book. There are no long derivations or numerical problems here. Instead, the unit shows how the physics you have already studied is used in new areas: making materials a few nanometres across, building robots, imaging and treating the human body, and studying the smallest particles and the largest objects in the universe.

The first half is practical. Nanotechnology explains why a lotus leaf stays dry and how nano-coatings and nano-medicines are made. Robotics describes what a robot is built from and where it is used. The medical physics section traces a line from Roentgen's X-rays in 1895 to MRI, CT and PET scans, capsule endoscopy, 3D printing and robotic surgery.

The last part moves to the extremes of size. Particle physics tells how protons and neutrons were found to be made of quarks held together by gluons, and how the Higgs particle was found. Cosmology covers gravitational waves and black holes. Because the unit is descriptive, questions tend to test definitions, names, dates and examples, so read the text carefully rather than skimming it.

What you'll learn

• Define the nanoscale and explain, using surface-to-volume ratio, why nanomaterials behave differently from bulk materials.
• Name the main parts of a robot and state what each part does.
• Describe the physical principle behind X-ray, CT and MRI imaging and list newer medical technologies from the textbook.
• Describe black holes and name Sagittarius A* and M87*.
• State the evidence for the Big Bang model and explain what gravitational waves are.
• Identify quarks, leptons, gluons and the Higgs particle as parts of the Standard Model.

Before you start

• Structure of the atom: electrons, protons and neutrons.
• The electromagnetic spectrum, especially X-rays and radio waves.
• Basic ideas of force, gravitation and motion from Class 11.

Recent Developments in Physics explained

What this unit covers

Nanoscience and Nanotechnology

One nanometre is \(10^{-9}\) m. Nanoscience studies materials whose size is roughly 1 to 100 nm in at least one dimension; nanotechnology uses that knowledge to make useful devices and products. At this size a much larger fraction of atoms sit on the surface, so the surface-to-volume ratio is very high. This changes colour, reactivity, strength and electrical behaviour compared with the bulk material. Nature already uses nanostructures: the lotus leaf repels water, and the colours of butterfly wings and peacock feathers come from nanoscale structures, not pigments. Nanomaterials are made by two routes: top-down (cutting a bulk material down to nano size) and bottom-up (building up from atoms and molecules).

Robotics

Robotics combines physics, mechanical and electrical engineering and computer science. Most robots have three main parts: a controller (the brain that runs the program), mechanical parts such as motors, pistons and grippers, and sensors that tell the robot about its surroundings. Actuators turn stored energy into motion. Robots range from human-like robots to industrial robots such as SCARA arms used for assembly. They are used in manufacturing, space and underwater exploration, defence and surgery, often in places that are dangerous for people.

Physics in Medical Diagnosis and Therapy

Medicine has used physics since Roentgen discovered X-rays in 1895. The textbook lists later milestones such as nuclear medicine, ultrasound, CT, MRI and PET. X-rays and CT use ionising radiation, while MRI uses a strong magnetic field and radio waves. Newer ideas in the unit include virtual reality, precision medicine, wireless capsule endoscopy, electronic health records, 3D printing of body parts, digital operation theatres and robotic surgery. In therapy, carefully aimed high-energy radiation destroys cancer cells while limiting damage to healthy tissue.

Black Holes

A black hole is the final stage of a very massive star: an extremely dense object whose gravity is so strong that nothing, not even light, can escape. Less massive stars end as white dwarfs or neutron stars instead. Most large galaxies are believed to have a supermassive black hole at the centre; the one in our Milky Way is Sagittarius A*. The first image of a black hole, M87*, was produced by the Event Horizon Telescope, a network of radio telescopes spread across the Earth that works like one Earth-sized telescope.

Cosmology and the Origin of the Universe

Cosmology studies the origin and evolution of the universe and the formation of stars and galaxies. The accepted picture is the Big Bang model: the universe began in a very hot, dense state and has been expanding ever since. Two pieces of evidence support it: distant galaxies are moving away from us, and the cosmic microwave background radiation fills all of space. Einstein predicted gravitational waves, ripples in space-time that travel at the speed of light, in 1915. LIGO detected them in 2015 from two merging black holes, and the discovery won the 2017 Nobel Prize.

Particle Physics

Once, the atom was thought to be indivisible. Then came electrons, protons and neutrons, and in the 1960s it was found that protons and neutrons are themselves made of quarks, held together by gluons. The Standard Model groups the elementary particles into quarks, leptons (such as the electron) and force-carrying bosons (such as the photon). The Higgs particle was found at CERN's Large Hadron Collider in 2012, and Peter Higgs and Francois Englert received the 2013 Nobel Prize for predicting it.

Common mistakes to avoid

• Mixing up nanoscience and nanotechnology. Nanoscience is the study of materials at the nanoscale; nanotechnology is the use of that knowledge to make things.
• Assuming a robot must look like a human. Most robots, such as industrial SCARA arms, are built for one specific job and look nothing like people.
• Writing that MRI uses X-rays or other ionising radiation. MRI uses a strong magnetic field and radio waves; it is CT that uses X-rays.
• Describing the Big Bang as an explosion of matter into empty space. It is the expansion of space itself from a hot, dense early state.
• Saying the Higgs particle was discovered in 2013. It was announced at CERN in 2012; the Nobel Prize to Higgs and Englert came in 2013.
• Thinking gravitational waves are sound waves or electromagnetic waves. They are ripples in space-time that travel at the speed of light.

Test yourself on these with the practice test, then check the worked reasoning in the solved MCQs.

Frequently asked questions

What is the difference between nanoscience and nanotechnology?

Nanoscience is the study of structures and materials on a scale of about 1 to 100 nanometres, where properties differ from the bulk. Nanotechnology is the design, production and application of devices and systems by controlling shape and size at that scale.

Why do nanomaterials have different properties from bulk materials?

When a particle becomes very small, a large share of its atoms lie on the surface, so the surface-to-volume ratio rises sharply. This makes it more reactive. At the nanoscale, quantum effects also change its optical, electrical and magnetic behaviour. Gold, for example, appears red or purple as nanoparticles instead of yellow.

How does a robot use sensors?

Sensors collect information about the surroundings, such as light, sound, touch or temperature, and send it to the controller. The controller processes this information according to its program and signals the actuators and motors to carry out the required movement.

Is radiation used in medicine always harmful?

No. Large doses of ionising radiation are harmful, but medical use is controlled. Imaging uses the smallest dose that gives a clear picture, and radiotherapy aims high-energy beams at cancer cells while sparing healthy tissue as far as possible. Some methods, such as MRI and ultrasound, use no ionising radiation at all.

What evidence supports the Big Bang model?

Distant galaxies are moving away from us, and the farther they are, the faster they recede, which shows the universe is expanding. The cosmic microwave background radiation, a faint glow left over from the hot early universe, is found in every direction.

What are the fundamental particles in the Standard Model?

Matter is made of quarks and leptons. Protons and neutrons contain quarks, and the electron is a lepton. Forces are carried by bosons: the photon for electromagnetism and gluons for the strong force, which binds quarks together. The Higgs particle is linked to the field that gives elementary particles their mass.