Light interacts with other forms of energy, such as heat and sound, through various mechanisms:
Heat: When light interacts with matter, it can be absorbed, reflected, or transmitted. The absorption of light can increase the energy of the matter, which manifests as an increase in temperature. This is how light energy is converted into heat energy. For example, when sunlight hits an object, the object absorbs some of the light energy and converts it into heat.
Sound: Light and sound are different forms of energy that interact differently. Light is an electromagnetic wave that does not require a medium to travel, whereas sound is a mechanical wave that requires a medium, such as air or water, to propagate. Light waves consist of varying electric and magnetic fields, while sound waves are compression waves caused by the vibration of particles in a medium. Generally, light and sound waves do not directly interact with each other, although they can both interact with matter separately.
Regarding the speed of light in a vacuum, it is a fundamental constant of nature and is denoted as "c." In a vacuum, where there is no matter to interact with, the speed of light remains constant. This constancy of light's speed in a vacuum is one of the fundamental principles of physics known as the "invariance of the speed of light." It is a postulate of Einstein's theory of special relativity.
In a vacuum, there are no particles or medium to significantly affect or slow down the propagation of light. Light waves can freely travel through a vacuum without being scattered or absorbed by particles. This is why the speed of light in a vacuum, approximately 299,792 kilometers per second (186,282 miles per second), remains unchanged and unaffected by interactions with other forms of energy.