Question

In ancient cemeteries bodies were not buried very deeply, and were often just wrapped in a sheet. As the soil dried out, sometimes there were ways for decomposition gases to reach the surface. These gases were denser than

air, and especially at night with no wind, would stay close to the grave. The result was a spooky “corpse light,” a kind of pale blue flamelike plume that appeared to rise out of the grave. It could be seen all night long, but tended to get dimmer as the hours went by. What physical process was involved?

1. Fluorescence.
2. Incandescence.
3. Pair annihilation.
4. Phosphorescence.
5. Lasing of a gas.
6. Stimulated emission.

Answer 1

I'll try to explain each of the phenomena, As they are pretty different from each other,

1) Incandescence - It is the emission of electromagnetic radiation (including visible light) from a hot body as a result of its temperature. This can be seen when an iron rod starts glowing if heated up to a certain temperature inside a furnace.

2) Pair annihilation -It occurs when an electron (e?) and a positron (e+, the electron's antiparticle) collide. The result of the collision at low energies is the annihilation of the electron and positron, and the creation of gamma-ray photons.

3) Lasing of a gas - It is a phenomenon in which an electric current is discharged through a gas to produce coherent light

4)Stimulated emission- It is the process by which an incoming photon of a specific frequency can interact with an excited atomic electron (or other excited molecular states), causing it to drop to a lower energy level.

5)Fluorescence- It is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. Fluorescent materials cease to glow nearly immediately when the radiation source stops, unlike phosphorescent materials, which continue to emit light for some time after

ANSWER - 6) Phosphorescence - It is a type of photoluminescence related to fluorescence. Unlike fluorescence, a phosphorescent material does not immediately re-emit the radiation it absorbs. The slower time scales of the re-emission are associated with "forbidden" energy state transitions in quantum mechanics. As these transitions occur very slowly in certain materials, absorbed radiation is re-emitted at a lower intensity for up to several hours after the original excitation.

Everyday examples of phosphorescent materials are the glow-in-the-dark toys, stickers, paint, and clock dials that glow after being charged with a bright light such as in any normal reading or room light. Typically, the glow slowly fades out, sometimes within a few minutes or up to a few hours in a dark room.