When is the speed of light a constant 299,792,458 meters per second

The speed of light is constant in vacuum and is equal to 299,792,258 meters per second.

Explanation:

The whole topic of constant speed of light is a bit misleading. The question that arises is:

Is the speed of light is constant everywhere? and if it is not constant everywhere, where does it change?

If we are talking about the interstellar space, the speed of light is constant everywhere in vacuum because astronomers do not need to consider speed of light in any media.

However, the speed of light changes when it goes from one medium to another. Like when light enters in a denser medium, its frequency remains constant but the wavelength decreases which is also the reason behind bending of light.

We know that the speed of light 'v' is given as:

v = fλ              where f = frequency and λ = wavelength

This equation implies that constant frequency and decrease in wavelength means decreased speed.

Similarly, the speed of light will increase when light travels from denser medium to a lighter medium as wavelength increases and frequency remains constant. As there is no medium lighter than vacuum, the speed of light is maximum there and is always constant.

freezing

deposition

condensation

explanation;

melting also called fusion is the process where solid becomes liquid, sublimation is the process where solid becomes gaseous without first changing to liquid, deposition involves change from gaseous to solid state, freezing involves change from liquid to solid, boiling or evaporation involves change of liquid to gaseous state, while condensation is the change from gaseous state to liquid state.

endothermic reactions involves absorption of heat from the surroundings or the environment while exothermic reactions involves loss of heat energy to the surroundings.

in this case, sublimation, evaporation and melting are endothermic reactions (gain energy from the environment) while, freezing, deposition and condensation are exothermic (loss of energy to the surroundings) reactions.

explanation:

earth's surface is mainly heated by the absorption of infrared radiation from the sun.

evaporation occurs because molecules in liquid water are warmed ( usually by the sun) and vibrate quicker, becoming less dense and rise.

condensation occurs because molecules in water vapor are cooled and therefore vibrate more slowly thus becoming more dense and eventually fall to earth.

lines of equal barometric pressure on a weather map are called: isobars : lines of equal temp on a weather map are called: isotherms.​