Laser vs. Light: How Are They Different?

Lasers have several attributes that make them different from conventional sources of light. These characteristics are the reason why it’s used in a wide range of applications including the medical sector, industrial production, computers, and music.

A lot of these applications employ laser technology because it’s more efficient than incandescent lighting. In the case of regular lights, a significant portion of the energy used to illuminate is lost in the form of heat.

But with lasers, the greatest portion of the energy used to generate light is in the beam, making it more efficient and powerful. Read on to learn more differences between laser and ordinary light.

Coherence

One of the primary differences between laser and ordinary light has to do with coherence. To understand this, consider the application of laser technology in barcode scanners used in supermarkets and grocery stores.

If you’re usually keen, you’ve noted how steady the beam of a light from the barcode scanner is. This steady and focused nature of light is what we refer to as coherence.

It means that the particles carrying light energy (photons) have the same frequency and that the waves have an identical phase relationship. Being in phase means that they move in sync with one another.

By comparison, ordinary light sources produce incoherent light. Simply put, the photons seem to travel in a rather chaotic manner. For instance, when you use a flashlight to illuminate a dark room, the light usually diffuses. This occurs because the photons have varying frequency and the waves are out of phase with each other.

Monochromatic

Another unique attribute of laser light is that it’s monochromatic. This term is derived from the Greek words: monos- which means one- and chromos - which means color. So in essence, laser light is of one color or wavelength.

You can notice this difference if you observe the sun, light bulbs or other conventional source of light, then compare to this to laser light. With bulbs, the light will appear to be “white” but it will have many wavelengths.

However, laser light will have a single, intense color. Depending on the laser device you’re using, this could be red, blue, green or yellow.

But why is this the case?

The reason is that laser light originates from a single atomic transmission. This means that the particles carrying light have equal energy and wavelength or frequency.

In contrast, the particles emitted from normal light sources possess different energies, frequencies, wavelengths and subsequently, result in different colors.

Directionality

Due to the mechanism used to produce laser light, the beams of this light are incredibly small, compact and bright. The light-carrying particles are moving almost parallel to one another.

If you were to shine a torch and a laser beam on the building across the street, they will have different patterns. The beam from the flashlight will appear to be wide while that of the laser will be very thin. This is because laser light has little divergence.

How Does It Work?

There are several ways of generating laser light. While some lasers use gas, there are those that use diodes or crystals. These beams of light also vary in size. Some are very tiny while others are big enough to illuminate a room.

Despite these differences, they all use the same principle, and that entails creating concentrated light by activating atoms with radiation. Let’s look at how one of the most common forms of laser, the gas ion laser, works.

A gas ion laser consists of a tube that’s filled with a noble gas such as argon or krypton. In some instances, the tube might have a combination of these gases.

A high voltage current is passed down this tube. This process causes the atoms of the gas inside the tube and the electrons from the current to collide. The collisions lead to the ionization of the gas atoms.

During this stage, some of the gas ions interact with a larger number of electrons, making them move to a higher energy state. However, they resume the lower energy state almost immediately. The quick transition from a high energy state to a lower one leads to the creation of photons. The photons collide with more gas ions, and this is the process that generates more concentrated light. The resulting light is monochromatic, coherent and highly directional.

Summary

Laser and regular lights are both types of light. But that is as far as their similarity goes. The truth is, these lights differ in many ways.

For instance, ordinary lights produce wide beams of light. Lasers, on the other hand, generate a precise wavelength of light, which is why they’re monochromatic.

Additionally, ordinary lights emit light in every direction. As a result, the light fills the entire space where it’s being illuminated. Conversely, lasers produce one very thin beam of light; hence they only illuminate a small section.

  • Updated October 16, 2019
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