Physics

Fast Breeder Reactors typically use mixed carbide fuels such as Uranium-Plutonium carbide because of their high breeding ratio and better thermal conductivity compared to oxides. While Uranium-Plutonium oxide is also used in some reactors, carbide fuel is more characteristic of fast breeder reactors.

The Aurora Borealis occurs when charged particles from the sun collide with gases in the Earth's ionosphere, causing the characteristic red and green lights. The ionosphere is the layer where these interactions primarily happen, not the troposphere, mesosphere, or stratosphere.

At ordinary temperatures, sound travels approximately 1120 feet per second. For an echo to be distinctly heard, the reflected sound must return after at least 0.1 seconds, meaning the reflecting surface must be at least 56 feet away (since sound travels to the surface and back, the total distance is 112 feet, so one way is 56 feet).

In nuclear reactions, fission is the process where a heavy nucleus splits into smaller nuclei, while fusion is the process where two or more light nuclei combine to form a heavier nucleus. Therefore, the reaction described where nuclei fuse to form a heavy nucleus is called fusion nuclear reaction.

Stealth technology primarily involves methods such as special coatings and design features that reduce an aircraft's radar cross-section, making it less visible to radar detection. Option B correctly identifies this as a coating that reduces radar visibility.

Approximately one third of an iceberg's volume remains above the water surface because ice is less dense than seawater. This means about two thirds of its mass is submerged, leaving roughly one third visible above water.

Myopia, or nearsightedness, occurs when the eye focuses images in front of the retina. It is corrected using a concave lens, which diverges light rays so they focus correctly on the retina.

To see her full image in a plane mirror, the minimum length of the mirror must be half her height, which is 3 feet for a 6 feet tall lady. This is because the angles of incidence and reflection allow the full image to be seen in a mirror half the person's height.

Weightlessness inside a spacecraft occurs because both the astronaut and the spacecraft are in free fall, effectively falling around the Earth together, which creates the sensation of zero weight. Gravity still acts on them, but there is no normal force acting on the astronaut.

When a train passes at high speed, the air pressure near the train decreases rapidly, creating a suction effect that tends to pull nearby objects, like the boy, towards the train, but the dominant effect is the air pushed forward causing the boy to be pushed away from the train. Hence, the boy is more likely to fall away from the train due to the air displacement.