Recent Trends in Physics
Class 12 Physics Notes • NEB Syllabus 2083
Syllabus, 10 solved multiple choice questions, descriptive answers with diagrams, handwritten and typed PDF notes and frequently asked questions on seismology, the Gorkha earthquake, gravitational waves, nanotechnology and the Higgs boson.
1. Syllabus
Unit: Modern Physics
Chapter 25: Recent Trends in Physics (2 hours)
These notes follow the NEB Class 12 Physics syllabus (+2 Physics, Nepal). Practise the multiple choice questions first, then work through the numericals, and finish with the PDF notes for quick revision.
2. Multiple Choice Questions
Question 1. Which type of seismic wave travels faster?
- a) surface wave
- b) Rayleigh wave
- c) S-wave
- d) P-wave
Correct Answer: d) P-wave
Reason: Primary waves (P-waves) are compressional longitudinal waves. They travel fastest through the Earth (about \(5\) to \(8\ \mathrm{km/s}\) in the crust) and arrive at a seismic station before any other wave.
Question 2. Who predicted the existence of gravitational waves?
- a) Newton
- b) Albert Einstein
- c) Peter Higgs
- d) Stephen Hawking
Correct Answer: b) Albert Einstein
Reason: Albert Einstein predicted gravitational waves in 1916 as a consequence of his general theory of relativity. Accelerating massive objects disturb space-time and send out ripples that travel at the speed of light.
Question 3. What kind of motion does a Love wave produce?
- a) elliptical rolling motion
- b) horizontal side-to-side motion
- c) vertical shaking
- d) back-and-forth compression
Correct Answer: b) horizontal side-to-side motion
Reason: Love waves are transverse surface waves. They move the ground horizontally, side to side, perpendicular to the direction in which the wave travels. This shearing action is very destructive to the foundations of buildings.
Question 4. The Higgs boson was confirmed through experiments at:
- a) NASA
- b) ISRO
- c) CERN (LHC)
- d) MIT
Correct Answer: c) CERN (LHC)
Reason: The Higgs boson was confirmed in 2012 by the ATLAS and CMS experiments at the Large Hadron Collider (LHC) of CERN, the European Organization for Nuclear Research, near Geneva.
Question 5. Which of the following seismic waves can travel through solids, liquids and gases?
- a) S-wave
- b) P-wave
- c) Rayleigh wave
- d) Love wave
Correct Answer: b) P-wave
Reason: P-waves are compressional waves: the particles move parallel to the direction of travel and the volume of the medium changes. Solids, liquids and gases can all be compressed, so P-waves pass through all three. S-waves need shear strength and travel only through solids.
Question 6. What is the speed of gravitational waves?
- a) 10,000 km/s
- b) speed of light
- c) half the speed of light
- d) variable, depending on the source
Correct Answer: b) speed of light
Reason: According to general relativity, gravitational waves travel at the speed of light in vacuum, \(c\approx3\times10^{8}\ \mathrm{m/s}\). This was confirmed in 2017 when gravitational waves and light from the merger of two neutron stars were detected together.
Question 7. What does the Higgs field do?
- a) binds electrons and protons
- b) causes gravitational attraction
- c) gives particles their mass
- d) generates dark energy
Correct Answer: c) gives particles their mass
Reason: The Higgs field is a field that fills the whole universe. Fundamental particles such as quarks and electrons acquire mass through their interaction with it (the Brout-Englert-Higgs mechanism).
Question 8. The region of initiation of seismic energy within the Earth is called the:
- a) epicentre
- b) hypocentre
- c) area of greatest building damage
- d) area of least building damage
Correct Answer: b) hypocentre
Reason: The hypocentre (focus) is the point inside the Earth where the fault rupture begins and the seismic energy is first released. The epicentre is the point on the surface directly above it.
Question 9. Which of the earthquake waves is first recorded on the seismograph?
- a) P-waves
- b) S-waves
- c) Rayleigh waves
- d) Love waves
Correct Answer: a) P-waves
Reason: P-waves have the highest speed of all seismic waves, so they reach a recording station first and appear first on the seismogram.
Question 10. Nanomaterials are materials with at least one dimension measuring less than:
- a) \(1\ \mathrm{nm}\)
- b) \(10\ \mathrm{nm}\)
- c) \(100\ \mathrm{nm}\)
- d) \(1000\ \mathrm{nm}\)
Correct Answer: c) \(100\ \mathrm{nm}\)
Reason: Nanomaterials are defined as materials having at least one dimension in the nanoscale, about \(1\ \mathrm{nm}\) to \(100\ \mathrm{nm}\), where \(1\ \mathrm{nm}=10^{-9}\ \mathrm{m}\).
3. Numerical and Subjective Questions
Seismology is the scientific study of earthquakes, of the elastic waves that travel through the Earth, and of the structure of the Earth’s interior revealed by these waves.
When energy is suddenly released in the Earth’s crust during an earthquake, it spreads out as elastic waves called seismic waves. They are of two main groups: body waves and surface waves.
Figure: Classification of seismic waves
i) Body waves
Body waves travel through the deep interior of the Earth.
ii) Surface waves
Surface waves travel along the surface of the Earth, and their amplitude decreases rapidly with depth. They are slower than body waves, but they carry more energy and cause most of the damage.
Figure: Particle motion in the four types of seismic waves
The Gorkha earthquake struck central Nepal on 25 April 2015 at 11:56 am (Nepal time).
i) Key seismic parameters
ii) Impact on different regions
iii) Why it was so destructive
Seismic waves are of four main types, according to their path and the motion of the particles:
Comparison:
| Parameter | P-wave | S-wave | Love wave | Rayleigh wave |
|---|---|---|---|---|
| Category | Body wave | Body wave | Surface wave | Surface wave |
| Particle motion | Alternate compression and expansion along the direction of the wave | Transverse vibration perpendicular to the direction of the wave | Horizontal, side to side | Elliptical rolling motion (vertical and horizontal) |
| Average speed | Fastest (about 5 to 8 km/s) | Intermediate (about 3 to 4.5 km/s) | Slow (about 2 to 4.4 km/s) | Slowest (about 2 to 4 km/s) |
| Medium | Solids, liquids and gases | Solids only | Solids only (shallow crust) | Solids only (near the surface) |
| Order of arrival | First | Second | Third | Fourth |
| Destructiveness | Low | Moderate | Very high (shears building foundations) | Very high (rolls the ground and collapses structures) |
i) Concept of the Higgs boson
The Higgs boson is an elementary particle of the Standard Model of particle physics. It is the quantum (excitation) of the Higgs field, a field that fills the whole universe.
Fundamental particles moving through space interact with this field, and the interaction gives them their mass. Particles that interact strongly with the field (such as the top quark) have a large mass, those that interact weakly (such as the electron) have a small mass, and particles that do not interact with it (such as the photon) are massless.
Figure: How the Higgs field gives mass to particles
ii) Importance in modern physics
iii) Discovery of the Higgs boson
i) Definition
Nanotechnology is the science, engineering and technology of the nanoscale, about \(1\ \mathrm{nm}\) to \(100\ \mathrm{nm}\) (\(1\ \mathrm{nm}=10^{-9}\ \mathrm{m}\)). It deals with the design, production and use of structures, devices and materials by controlling matter at the level of atoms and molecules. At this scale quantum effects become important, and materials show new physical, optical, chemical and electrical properties.
ii) Brief history
iii) Four major fields of application
4. View PDF Notes
i. Handwritten Notes
ii. Typed PDF Notes
5. Frequently Asked Questions
What are the recent trends in physics? (Class 12 notes)
What topics are included in Chapter 25 Recent Trends in Physics of NEB Class 12 Physics?
Is Recent Trends in Physics a Class 11 or Class 12 chapter?
What is seismology?
What are the types of seismic waves?
What are the epicentre and the hypocentre of an earthquake?
What were the key parameters of the Gorkha earthquake of 2015?
What is a gravitational wave?
What is nanotechnology?
What is the history of nanotechnology?
What is the Higgs boson?
Why is the Higgs boson important in physics?
Which seismic wave is recorded first on a seismograph and which is most destructive?
Where can I get Class 12 Physics Chapter 25 Recent Trends in Physics notes in PDF?
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