Tag: science & technology

Sri Lanka celebrates its Independence Day on February 4, 1948, when the country gained independence from British rule. This is the correct and historically accurate date.

The United States celebrates its Independence Day on July 4, 1776, commemorating the adoption of the Declaration of Independence. This is the foundational date of American nationhood.

In a plane mirror, a virtual image is formed because the reflected rays diverge and appear to originate from a point behind the mirror. The image is also upright. Since all these characteristics describe the virtual image formation, 'all of the above' is correct.

Fiber optic cables transmit light through total internal reflection, where light travels through the core by repeatedly reflecting off the cladding boundary at angles greater than the critical angle. This principle allows signals to travel long distances with minimal signal loss. Dispersion and magnification are optical phenomena but not the transmission mechanism, and intensification doesn't occur.

Gamma rays have the highest frequency in the electromagnetic spectrum, ranging from 10^19 Hz and above. They are produced by radioactive decay, nuclear explosions, and cosmic events. The electromagnetic spectrum in order of increasing frequency is: radio waves, microwaves, infrared, visible light, UV, X-rays, and gamma rays.

Sound is a mechanical wave that requires a medium (solid, liquid, or gas) to propagate and is not an electromagnetic wave. Light, radio waves, and X-rays are all electromagnetic waves that can travel through vacuum. Electromagnetic waves are oscillations of electric and magnetic fields, while sound is a pressure wave.

According to the law of reflection, the angle of incidence always equals the angle of reflection when measured from the normal (perpendicular line) to the mirror surface. This is a fundamental principle of geometric optics.

J.J. Thomson discovered the electron in 1897 through cathode ray tube experiments. He determined that cathode rays were negatively charged particles much smaller than atoms, which he called 'corpuscles' - later named electrons.

Galileo made multiple significant contributions: he developed the telescope for astronomical use (not invented it), discovered four of Jupiter's moons (Io, Europa, Ganymede, Callisto), and discovered pendulum isochronism. Option D 'All are correct' appropriately acknowledges all his achievements.

Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth. The term derives from the Greek 'seismos' (earthquake) and 'logia' (study of). Seismologists analyze seismic waves to understand Earth's internal structure.