The imaging principle of concave mirror

The law of reflection of light states that the reflected light is in the same plane as the incident light and the normal, and the reflected light and the incident light are separated on both sides of the normal. The reflection angle is equal to the incident angle. When light shines on a concave mirror, it will reflect according to the law of reflection.
We can consider a concave mirror as a combination of countless small flat mirrors. The situation is quite special for the light emitted by a point light source on the central axis (also known as the main optical axis) of a concave mirror. For example, light rays parallel to the main optical axis directed towards a concave mirror will converge at a point after reflection, which is called the focal point (F). According to the principle of optical path reversibility, the light emitted from the focal point will be reflected by a concave mirror and emitted parallel to the main optical axis.
The light emitted from a certain point on an object will also converge and form an image after being reflected by a concave mirror. If an object is located outside the focal point of a concave mirror, the resulting image is a real image. The characteristic of a real image is that it is formed by the actual convergence of light, which can be received by a light screen. When an object moves away from a concave mirror, the image gradually approaches the focal point and the size of the image gradually decreases.
For example, a solar stove utilizes the principle of concave mirrors to converge parallel light. The sunlight can be approximated as parallel light, which shines on a concave mirror shaped solar stove and converges at the focal point after reflection. Placing the object to be heated at the focal point can utilize the concentrated solar energy for heating.
If an object is located within the focal point of a concave mirror, the resulting image is a virtual image. Virtual images cannot be captured by a light screen. The principle by which the human eye sees virtual images is that the reverse extension lines of reflected light converge into virtual images. In this case, the image is larger than the object, and the closer the object is to the focal point, the larger the image.
For example, makeup mirrors are usually concave mirrors. When a person's face is close to the makeup mirror (within the focus), what they see is a magnified virtual image, which helps them observe the details of their face more clearly, such as eyelashes, pores, etc.
The principle of concave mirror imaging has applications in many fields. In astronomical telescopes, concave mirrors can be used to converge the faint light emitted by distant celestial bodies, helping astronomers better observe celestial bodies. In car headlights, concave mirrors can reflect the light emitted by the bulb into parallel light, allowing the light to shine further and brighter, enhancing the lighting effect. In short, the application of concave mirror imaging principle is widespread, bringing many conveniences to our lives and scientific research.