What is the combustion of magnesium powder?

When photographers take photos in poor light, they often turn on the flash in order to increase the exposure intensity. The moment the shutter is pressed, the flash emits a dazzling beam of light, which flashes away and the photo is taken.

When people take photos with insufficient light intensity, the film will not be sensitive enough, and the photos taken will turn black. After using the flash, the strong light emitted by the flash enhances the light of the environment and objects, increasing the exposure of the film. Sometimes, even at night, the bright light from a flash can allow a camera to capture a clear scene. Why does the camera emit a brief bright light?

In the past, camera flashes mainly relied on burning magnesium and aluminum to produce flash. Originally, people mixed magnesium powder and potassium chlorate to make glittering materials. Originally, the reaction between magnesium and oxygen is slow at room temperature, but at high temperatures, the reaction between magnesium powder and oxygen is very violent. When people use a flash, magnesium powder burns violently in oxygen, generating a large amount of heat and emitting dazzling white light. The oxygen produced by the decomposition of potassium chlorate at high temperature accelerates the burning of magnesium powder, and the entire reaction time does not exceed 0.1 seconds. However, magnesium powder is more expensive and burning magnesium is unsafe, so people invented a flashlight that burned aluminum powder. People seal aluminum foil and oxygen in a glass container. When taking pictures, the aluminum foil is heated and reacts with oxygen to form a white aluminum oxide solid, which emits strong white light and fully exposes the film. Similar to magnesium powder, a flash made of aluminum foil only lasts less than a tenth of a second. Since these flash lamps rely on burning magnesium and aluminum to emit light, the flash lamp must be replaced with fuel.

The flashlights used today are all electronic flashlights. They are different from the flashlights of the past. They do not rely on the combustion of magnesium powder or aluminum foil to emit light. They rely on the light energy converted from the electrical energy of the battery in the camera to emit light. Therefore, the electronic flash can be used continuously. The flash time of electronic flash is shorter, only one thousandth of a second, so it is no wonder that the flash flashes and disappears.