Understanding Electromagnetic Waves: Properties, Uses, and Applications
Electromagnetic Waves: Properties and Applications
How Electromagnetic Waves are Produced
Electromagnetic waves are produced by the vibration of electrically charged particles. When a charged particle vibrates or moves back and forth, the electric field around it also vibrates. This vibrating electric field, in turn, produces a vibrating magnetic field. These two vibrating fields together generate an electromagnetic wave.
Speed of Electromagnetic Waves in a Vacuum
All electromagnetic waves travel at the same speed in a vacuum. This is because the speed of a wave is related to its wavelength and frequency by the following equation:
Speed of a wave = Wavelength * Frequency
Therefore, electromagnetic waves with different wavelengths can travel at the same speed as long as their frequencies are also different.
Categories of Electromagnetic Waves
Here are five categories of electromagnetic waves that all travel at the same speed in a vacuum:
- Radio waves
- Microwaves
- Infrared waves
- Visible light
- Ultraviolet light
X-rays and gamma rays are also categories of electromagnetic waves.
Sound Quality: AM vs. FM
FM radio waves are less affected by electrical noise than AM radio waves, which is why music broadcast on FM has better sound quality.
Advantages of AM Radio
AM radio waves have longer wavelengths than FM radio waves. This allows AM radio waves to bounce off the atmosphere and travel farther than FM radio waves.
Uses of Microwaves
Three common uses of microwaves are:
- Microwave ovens
- Cellular phones
- Radar
How Night Vision Works
Night vision devices, such as infrared binoculars, detect infrared waves and convert them into visible light. This allows users to see objects and animals in the dark due to their temperature differences.
Uses of Ultraviolet Light
Two uses of ultraviolet light are:
- Killing bacteria on food and surgical tools
- Stimulating the production of vitamin D in skin cells
Uses of X-rays
Two uses of X-rays are:
- Medical imaging
- Security screening in airports and public buildings
Uses of Gamma Radiation
Two uses of gamma radiation are:
- Treating some forms of cancer
- Killing harmful bacteria in food
The Law of Reflection
The law of reflection states that the angle of incidence (the angle at which a beam of light hits a surface) is equal to the angle of reflection.
Why the Sky is Blue
The sky appears blue due to a phenomenon called scattering. Light with shorter wavelengths, such as blue light, is scattered more than light with longer wavelengths. Sunlight is made up of many different colors, but blue light is scattered the most, creating a blue background in the sky.
Why We See Rainbows
Rainbows are created when sunlight is refracted (bent) by water droplets. White light is separated into different colors during refraction because different wavelengths of light bend at different angles. Shorter wavelengths, such as blue and violet, bend more than longer wavelengths, such as red and orange.
Transparency, Translucency, and Opacity
- Transparent: Allows light to pass through completely, allowing clear images to be seen.
- Translucent: Allows light to pass through, but scatters it, so images are not clear.
- Opaque: Does not allow light to pass through.
Electromagnetic Waves and Fields
Electromagnetic waves are made of changing electric and magnetic fields that are perpendicular to each other.
The transfer of energy as electromagnetic waves is called radiation.
TV stations use radio waves to carry both sound and pictures. Specifically, they use FM (frequency modulation) for sound and AM (amplitude modulation) for pictures.
- Electromagnetic wave: A wave that consists of electric and magnetic fields that vibrate at right angles to each other.
- Electric field: Surrounds every charged object, attracting oppositely charged objects and repelling like-charged objects.
- Magnetic field: Surrounds every magnet.
- Modulation: Changing amplitude or frequency.
- AM: Amplitude modulation.
- FM: Frequency modulation.
- Reflection: The bouncing of a beam of light when it hits a surface it does not pass through.
- Absorption: The transfer of light energy to particles of matter.
- Scattering: An interaction of light with matter that causes light to change its energy, direction of motion, or both.
- Refraction: The bending of a wave as it passes between two substances in which the speed of the wave differs.
- Transmission: The passing of light or other forms of energy through matter.
- Speed of a wave: Wavelength * Frequency.
- One nanometer (nm): Is equal to 1 * 10-9 m.
Additional Facts about Light and Waves
- Prisms produce the colors of the rainbow through refraction.
- Electromagnetic waves are made of magnetic fields and electric fields.
- You see yourself clearly in a mirror due to regular reflection.
- All electromagnetic waves travel at the same speed in a vacuum.
- Objects that transmit light easily are transparent.