Introduction to Light
Introduction to Light
This lesson aligns with NGSS PS4.B
Introduction
Light is a fundamental form of electromagnetic radiation. Like sound, like is a form of energy that propagates as a wave. However, in contrast to sound, light does not depend on a medium to transmit its energy and can travel through a vacuum. The primary source of light on earth is the sun, a colossal, blazing star that provides the radiant energy necessary for life to thrive. Artificial sources of light, such as light bulbs and LED lights have transformed our modern life. In this article, we will learn about what is light, how light is produced, and the speed of light.
What is light?
Light is an electromagnetic wave (EM wave), characterized by its ability to travel through both space and matter. It consists of changing electric and magnetic fields.
A field refers to a region around an object that can exert a force, such as push or pull, on another object without any physical contact. For instance, a magnet possesses a magnetic field capable of attracting a paper clip without direct touch. It is important to note that these fields, including the electromagnetic field of light, do not consist of matter but rather influence the interactions between objects in their surroundings.
Figure 1 illustrates that the electric and magnetic fields are positioned at right angles to each other. Furthermore, these fields are also perpendicular to the wave’s direction of motion. As a result of this arrangement, electromagnetic waves are categorized as transverse waves.
How Light is Produced?
The generation of an electromagnetic wave happened by the vibrations of electrically charged particles. Whenever a particle possesses an electric charge, an electric field surrounds it. As the charged particle vibrates or oscillates, the electric field also undergoes vibrations. Consequently, the vibrational motion of the electric field gives rise to a corresponding vibrating magnetic field. These combined vibrations of the electric and magnetic fields result in the creation of an electromagnetic wave, which serves as a carrier of the energy released during the initial particle’s vibration. This process of emitting energy in the form of EM waves is known as radiation.
Consider the following example to better understand how light is produced. Imagine turning on a lamp. The electrical energy provided to the filament within the bulb prompts the atoms in the filament to vibrate. Charged particles within these atoms also begin to vibrate, leading to the production of light.
- Electrons are negatively charged particles inside an atom that move around the nucleus at different distances based on their energy levels. When an electron absorbs energy, it can jump to a new position within the atom.
- This transition to a new position is usually unstable, and the electron may not be stable in that location. Eventually, the electron returns to its original position, releasing the absorbed energy in a tiny packet called a photon.
- The oscillation of electrons back and forth gives rise to a continuous flow of photons. This stream of photons can be considered as waves of vibrating electric and magnetic fields. The stream of photons carries the energy released by the electrons during their movement.
The Speed of Light
Scientists have not yet discovered anything in the universe that surpasses the speed of light. In the near space of the cosmos, the speed of light measures approximately 300,000,000 meters per second (m/s). light slightly slower when passing through substances such as air, glass, and other types of matter. Remarkably, light can travel more than 880,000 times faster than sound. To put this speed into perspective, if you could run at the speed of light, you could circle the earth 7.5 times in just one second.
Summary
- Light is an electromagnetic wave (EM wave) that can travel through both space and matter. It consists of changing electric and magnetic fields.
- When a charged particle oscillates, the electric field also undergoes vibrations. As a result, it gives rise to a corresponding vibrating magnetic field.
- The combined vibration of an electric field and a magnetic field produces an electromagnetic wave that carries energy released by the initial vibration of the particle. The emission of energy in the form of EM waves is known as radiation.
- The speed of light measures approximately 300,000,000 meters per second (m/s).
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