* Emission spectrum: This type of spectrum is produced when atoms or molecules are excited to a higher energy level and then emit photons of light as they return to their original energy level. Emission spectra are characteristic of each element or molecule, and can be used to identify the presence of specific substances.

* Absorption spectrum: This type of spectrum is produced when atoms or molecules absorb photons of light, causing them to transition to a higher energy level. Absorption spectra are also characteristic of each element or molecule, and can be used to identify the presence of specific substances.

* Continuous spectrum: This type of spectrum is produced by a source that emits light at all wavelengths. Continuous spectra are not characteristic of any particular element or molecule, and are instead produced by objects such as the sun or a light bulb.

The conditions that would cause us to see each of these three basic types of spectra are as follows:

* Emission spectrum: Emission spectra are produced when atoms or molecules are excited to a higher energy level. This can be done by heating the substance, exposing it to an electric current, or irradiating it with light.

* Absorption spectrum: Absorption spectra are produced when atoms or molecules absorb photons of light. This can occur when the substance is exposed to light, or when it is heated to a high enough temperature.

* Continuous spectrum: Continuous spectra are produced by objects that emit light at all wavelengths. This can occur when the object is heated to a high enough temperature, or when it is exposed to an electric current.