Because the light emitted by flashlights and sunlight can be approximately regarded as rays; Only a straight line that starts from a point and extends infinitely in one direction can be called a ray. A line segment has two endpoints and a length. A line that can only extend indefinitely in one direction can be called a ray.
The source of flashlight
1, flashlight is a hand-held electronic lighting tool, and its history can be traced back to the end of19th century. Early flashlights were called "flashlights", which means short-lived lamps, because their batteries were insufficient and their brightness was very limited. As a portable electronic lighting tool, flashlight has been widely used and popularized in the past decades.
2. The inventor of flashlight is Conrad Hubert, an inventor who immigrated from Russia to the United States. Hubert invented the first flashlight at the end of19th century, which consists of a battery-powered light bulb and a focusing lens. This invention is regarded as the prototype of flashlight and patented in 1899.
Before the invention of flashlight, people mainly relied on traditional light sources such as flashlight and candle. These traditional light sources have many limitations, such as low brightness, short service life and easy to cause fire. In contrast, flashlight has many advantages, such as high brightness, convenient use, safety and reliability. Therefore, flashlights have been widely used and rapidly popularized.
With the continuous development of science and technology, flashlights are constantly improved and upgraded. Today's flashlight is no longer a single lighting tool, but is developing in the direction of multi-function. Modern flashlights have many functions, such as waterproof, anti-fall, high temperature resistance and long battery life, which meet the needs of different users.
Flashlight is also widely used in many fields. For example, in outdoor adventure, night driving, night work and other scenes, flashlights can provide lighting and security. In the medical field, flashlights are also used in operating rooms, ambulances and other occasions to provide convenient lighting tools for medical staff.