Overview of electromagnetic wave
    Electromagnetic Wave (Electromagnetic Wave) is a wave caused by alternating changes in electric and magnetic fields, which can propagate in a vacuum. Electromagnetic waves do not require a medium, so they can propagate in a vacuum, unlike sound waves, mechanical waves, etc., which require a medium to propagate. Electromagnetic wave is one of the basic fluctuations in nature, which is widely used in various fields such as communication, medical treatment and scientific research.
Composition of electromagnetic wave
    Electromagnetic waves are fluctuations caused by electric and magnetic fields that are perpendicular to each other and propagate together. They have the following characteristics:
    Electric field: The changing electric field in electromagnetic waves oscillates at a certain frequency and affects the surrounding charged particles.
    Magnetic field: The magnetic field perpendicular to the electric field is also constantly changing, and also affects the motion of charged particles.
    Propagation direction: electric and magnetic fields are perpendicular to each other, and the propagation direction of electromagnetic waves is perpendicular to the direction of electric and magnetic fields.
    The propagation of electromagnetic waves does not depend on the medium; they can travel in a vacuum, which is why light can travel from the sun to the Earth.

Classification of electromagnetic waves

    Electromagnetic waves can be divided into a number of different types according to their frequency and wavelength, from low to high frequency sorted as follows:
    Radio Waves: Used for radio, television broadcasting, satellite communications, etc.
    Microwaves: Used in microwave ovens, radar, satellite communications, etc.
    Infrared: Used for thermal imaging, remote control, night vision, etc.
    Visible Light: Light waves that can be perceived by the human eye, with wavelengths of about 400nm to 700nm.
    Ultraviolet (Ultraviolet) : has a high frequency, can cause skin sunburn, has a disinfection effect.
    X-ray (X-ray) : Used in medical imaging, strong penetration.
    Gamma Rays: Extremely high frequency and energy, often used in nuclear reactions and radiation therapy.

Common problems of electromagnetic wave
Is electromagnetic wave harmful to human body?
    Whether electromagnetic wave is harmful to human body mainly depends on its frequency and energy. Low frequency electromagnetic waves (such as radio waves, microwave) usually do not cause direct harm to the human body, but high frequency electromagnetic waves (such as ultraviolet, X-ray, gamma rays) because of its strong energy, may cause damage to human tissues, and even cause health problems such as cancer. Reasonable radiation protection measures can effectively reduce the harm.

How fast does electromagnetic wave travel?
    Electromagnetic waves travel at the speed of light in a vacuum, that is, about 3×10? Meters per second. The speed of propagation in different media will vary, for example in water or glass, the speed of electromagnetic waves will be slower than in a vacuum.

What is the relationship between electromagnetic wave energy and frequency?
    E=h?f
    among
    E is energy, okay? h is Planck's constant (6.626×10? 346.626 x 10? 34),
    f is the frequency of an electromagnetic wave. The higher the frequency, the stronger the electromagnetic wave's energy.
    f is the frequency of an electromagnetic wave. The higher the frequency, the stronger the electromagnetic wave's energy.

What is electromagnetic radiation?

    Electromagnetic radiation refers to the process of electromagnetic waves being emitted from objects. All objects with temperatures above zero radiate electromagnetic waves in different ways. Hot objects (such as the sun) mainly emit visible and ultraviolet light, while cold objects (such as humans) mainly emit infrared light.

What is Electromagnetic Interference (EMI)?

    Electromagnetic interference (EMI) ** means that the normal operation of electronic devices is affected due to the interference of electromagnetic waves. EMI can come from the emission, propagation or reception of electromagnetic waves, which can affect devices such as mobile phones, computers, televisions, radar, and radio. In order to reduce electromagnetic interference, shielding, grounding and other technologies are usually used to protect equipment.

What is the relationship between electromagnetic wave and light?
    Light is a form of electromagnetic wave, specifically, it is the visible wave band. The frequency of the light wave is about 430 THz to 770 THz, and the wavelength is about 400 nm to 700 nm. Although light waves belong to electromagnetic waves, due to the particularity of frequency and wavelength, it is an electromagnetic wave that the human eye can perceive.

Can electromagnetic waves penetrate objects?

    The penetration of electromagnetic waves depends on the wavelength and frequency. For example, radio waves can penetrate buildings, while X-rays and gamma rays can penetrate many substances (including the human body and metals). Visible light and ultraviolet light are relatively weak and cannot penetrate opaque objects.

How to prevent electromagnetic radiation harm?
    In order to avoid the potential harm of electromagnetic waves to the human body, the following measures can be taken:
    Avoid prolonged close contact with strong electromagnetic radiation sources (such as high-power emission devices).
    Use electromagnetic shielding devices (such as metal mesh covers, shielding materials, etc.).
    Wear radiation protective equipment (such as radiation protective clothing, shielding glasses, etc.) in high frequency radiation environment.

What is the relationship between electromagnetic wave and communication technology?
    Electromagnetic wave is the basis of modern communication technology. Wireless communications, satellite communications, Wi-Fi, Bluetooth, mobile communications (such as 4G, 5G), etc., all rely on the propagation of electromagnetic waves. Electromagnetic waves in different frequency bands can be used for different communication tasks, and selecting suitable frequency bands and technologies can improve the data transmission rate and transmission distance.