Physics

The candela is the SI base unit of luminous intensity, which measures the perceived power of light emitted in a particular direction. It is not related to heat, temperature, or radioactive decay.

The mass of the Sun is approximately 1.989 × 10^30 kilograms, which is the widely accepted scientific value according to authoritative sources such as NASA and Britannica. This corresponds to option B. The originally stated value of 1.5 × 10^30 kilograms (option A) is incorrect and underestimates the Sun's mass.

The Karman line, located at an altitude of 100 kilometers above Earth's sea level, is internationally recognized as the boundary between Earth's atmosphere and outer space.

The Tesla (T) is the SI unit of magnetic flux density or magnetic field strength, named after Nikola Tesla. It measures the strength of a magnetic field.

An intrinsic semiconductor is a pure semiconductor without any significant impurities, so it is also known as a pure conductor in the context of semiconductors.

The temperature at the center of the Sun is approximately 15 million degrees Celsius, which is the core temperature where nuclear fusion occurs. This value is widely accepted in astrophysics based on solar models and observations.

The siemens (S) is the SI unit of electrical conductance, which measures how easily electricity flows through a conductor. It is the reciprocal of electrical resistance, measured in ohms.

In an atom, the total energy of a revolving electron is negative because it is bound to the nucleus; the energy is lower than that of a free electron at rest (which is zero). Therefore, the total energy can never be positive.

The SI unit of time, the second, is defined based on the frequency of radiation emitted by the transition between two hyperfine levels of the ground state of the cesium-133 atom, but historically it was defined using the frequency of light emitted by krypton-86. Among the given options, the frequency of light emitted by Kr86 is the closest and historically relevant definition.

The speed of light in a medium generally decreases as the temperature of the medium rises because the refractive index of the medium changes with temperature, typically increasing, which slows down light propagation.