What, then, is so different about the light from a laser?
The answer is in this chapter.
Soon after lasers were invented in the 1960s, they became novel sources of light in research laboratories. Today, lasers are ubiquitous and are found in such diverse applications as voice and data transmission, surveying, welding, and grocery-store price scanning. The photograph shows surgery being performed with laser light transmitted via optical fibers. Light from a laser and light from any other source are both due to emissions by atoms.
In this chapter we continue with a primary goal of physics—discovering and understanding the properties of atoms. About 100 years ago, researchers struggled to find experiments that would prove the existence of atoms. Now we take their existence for granted and even have photographs (scanning tunneling microscope images) of atoms. We can drag them around on surfaces, such as to make the quantum corral shown in the opening photograph of Chapter 39. We can even hold an individual atom indefinitely in a trap (Fig. 40-1) so as to study its properties when it is completely isolated from other atoms.
You may think the details of atomic physics are remote from your daily life. However, consider how the following ...