The mass density of a material varies with temperature and pressure. Increasing the temperature of a substance (with some exceptions) decreases its density by increasing the volume of that substance. In most materials, heating the bottom of a fluid results in convection of the heat from bottom to top of the fluid due to the decrease of the density of the heated fluid.

Correct Option: A

The mass density of a material varies with temperature and pressure. Increasing the temperature of a substance (with some exceptions) decreases its density by increasing the volume of that substance. In most materials, heating the bottom of a fluid results in convection of the heat from bottom to top of the fluid due to the decrease of the density of the heated fluid.

Many contemporary uses of uranium exploit its unique nuclear properties. Uranium-235 has the distinction of being the only naturally occurring fissile isotope. Uranium-238 is fissionable by fast neutrons, and is fertile, meaning it can be transmuted to fissile plutonium-239 in a nuclear reactor. Another fissile isotope, uranium-233, can be produced from natural thorium and is also important in nuclear technology.

Correct Option: B

Many contemporary uses of uranium exploit its unique nuclear properties. Uranium-235 has the distinction of being the only naturally occurring fissile isotope. Uranium-238 is fissionable by fast neutrons, and is fertile, meaning it can be transmuted to fissile plutonium-239 in a nuclear reactor. Another fissile isotope, uranium-233, can be produced from natural thorium and is also important in nuclear technology.

Persistence of vision is the phenomenon of the eye by which an afterimage is thought to persist for approximately one twenty-fifth of a second on the retina. Persistence of vision is still the accepted term for this phenomenon in the realm of cinema history and theory. In the early days of film innovation, it was scientifically determined that a frame rate of less than 16 frames per second (frame/s) caused the mind to see flashing images.

Correct Option: C

Persistence of vision is the phenomenon of the eye by which an afterimage is thought to persist for approximately one twenty-fifth of a second on the retina. Persistence of vision is still the accepted term for this phenomenon in the realm of cinema history and theory. In the early days of film innovation, it was scientifically determined that a frame rate of less than 16 frames per second (frame/s) caused the mind to see flashing images.

According to the Archimedes’ principle, a floating object will experience an upthrust force from water, equal to the weight of water displaced (pushed aside). It will sink into the water until it reaches the point where the weight of the water pushed aside equals its own weight. For an object that is floating, the mass of the material equals the mass of water that is displaced by the object (1 kg = 1 L of water). Dense objects cannot displace enough water to provide an upthrust force to counterbalance their weight, so they plummet below the surface. Objects made of material denser than water (e.g. a boat made of iron) can still float if they contain air so that the mean density is less than that of water. The upthrust is often called the loss in weight of the object. Upthrust = apparent loss of weight of object = weight in air - weight in liquid.

Correct Option: B

According to the Archimedes’ principle, a floating object will experience an upthrust force from water, equal to the weight of water displaced (pushed aside). It will sink into the water until it reaches the point where the weight of the water pushed aside equals its own weight. For an object that is floating, the mass of the material equals the mass of water that is displaced by the object (1 kg = 1 L of water). Dense objects cannot displace enough water to provide an upthrust force to counterbalance their weight, so they plummet below the surface. Objects made of material denser than water (e.g. a boat made of iron) can still float if they contain air so that the mean density is less than that of water. The upthrust is often called the loss in weight of the object. Upthrust = apparent loss of weight of object = weight in air - weight in liquid.

A lighthouse is a tower, building, or other type of structure designed to emit light from a system of lamps and lenses and used as an aid to navigation for maritime pilots at sea or on inland waterways. Lighthouses mark dangerous coastlines, hazardous shoals, reefs, safe entries to harbors, and can also assist in aerial navigation. Once widely used, the number of operational lighthouses has declined due to the expense of maintenance and replacement by modern electronic navigational systems.

Correct Option: D

A lighthouse is a tower, building, or other type of structure designed to emit light from a system of lamps and lenses and used as an aid to navigation for maritime pilots at sea or on inland waterways. Lighthouses mark dangerous coastlines, hazardous shoals, reefs, safe entries to harbors, and can also assist in aerial navigation. Once widely used, the number of operational lighthouses has declined due to the expense of maintenance and replacement by modern electronic navigational systems.