What's the name of that spot that lights up in the sky at night?
Role: first, pilot lights, to prevent aircraft hit high-rise buildings; two is to decorate the city's beauty.
It can use a mirror or lens to focus the injection beam in a very small solid angle (usually less than 2 degrees) to obtain a larger light intensity.
Searchlight。A searchlight is a device with a powerful light source and a concave mirror that focuses light on a specific direction for use in remote lighting and searching.
