Which of the following is one of the mediums commonly used with lasers?

Lasers operate based on the principle of stimulated emission of radiation, and the specific medium used plays a critical role in generating the laser light. In this case, gas is indeed one of the common mediums used with lasers. Gas lasers utilize a gas as the medium for producing laser light, which can include various types of gases, such as helium-neon or carbon dioxide.

Gas lasers work by passing an electric current through the gas, which excites the molecules and, when they return to a lower energy state, they emit photons (light). This process is highly efficient and allows for a range of wavelengths, making gas lasers versatile for various applications in medical and cosmetic settings.

While liquids, solids, and plasma can also be involved in other types of lasers, gas as a medium is particularly significant and widely recognized in the context of laser technology. Understanding the specific roles and characteristics of different mediums helps to clarify the principles, applications, and functionalities of various lasers in esthetic practices.