Physics

A black body is defined as an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence, without reflecting any. Therefore, it absorbs all radiation entering it.

If the x-component (Ax) of a vector is negative and the y-component (Ay) is positive, the vector lies in the 2nd quadrant. This is because in the Cartesian coordinate system, the 2nd quadrant is defined by negative x-values and positive y-values. Therefore, the correct answer is option A (2nd quadrant). The original correct_answer 'C' (3rd quadrant) is incorrect.

An open system can exchange both matter and energy with its surroundings, unlike closed systems (which exchange only energy) or isolated systems (which exchange neither).

When a projectile moves upward, the vertical component of its velocity decreases due to the acceleration of gravity acting downward, slowing the upward motion until it reaches zero at the peak.

An LED (Light Emitting Diode) is a forward-biased pn-junction device that emits light when current flows through it. A photodiode, on the other hand, is essentially the reverse-biased counterpart of an LED. It operates with reverse polarity and converts incident light (photons) into an electrical current flowing in the opposite direction to the forward current of an LED. When light strikes the reverse-biased photodiode, electron-hole pairs are generated, producing a photocurrent. This makes the photodiode effectively the 'reverse' of an LED in terms of function and operation mode.

Entropy is measured in joules per kelvin (J/K), representing energy dispersal per unit temperature. This unit correctly reflects the physical dimension of entropy.

Optical fiber transmission uses monochromatic light because it minimizes dispersion and attenuation, allowing signals to travel longer distances with less distortion.

In the CGS (centimeter-gram-second) system, the unit of force is the dyne, defined as the force required to accelerate a mass of one gram at a rate of one centimeter per second squared. Newton and pound are units from other systems (SI and Imperial respectively).

Inertia is the property of an object to resist changes in its state of motion, and it depends solely on the mass of the object. Neither velocity, direction, nor time affects inertia.

The modern system of navigation satellites is called Navstar, which is the official name for the Global Positioning System (GPS). The other options are unrelated to satellite navigation systems.