What is the principle of light when we read and write under the light at night?

At night, we use the principle of light reflection to read and write under the light, from desk lamp to book, and then from book to eyes.

Law of light reflection: reflected light and incident light are on the same plane as the normal; Reflected light and incident light are separated on both sides of the normal; The reflection angle is equal to the incident angle. It can be summarized as: "Three lines * * * plane, two lines are separated, and the two angles are equal." Light is reversible. In the phenomenon of light reflection, the optical paths are equal.

Examples of light reflection:

Mirror. Due to the reflection of light, the mirror can reflect the received light and make people see themselves in the mirror.

The rearview mirror of a car also uses the principle of light reflection. The rearview mirror of the car is concave, and the scenery behind it will shrink when it is reflected back to the human eye, so you can see a large area of the scenery behind it in the small mirror.

Signs on expressways are all made of "retro-reflective films". When driving at night, you can reverse the light from the headlights, so the words on the sign are particularly eye-catching.

Different reflection effects of various curved surfaces on light can make light converge or diverge. The reflector in a flashlight uses this principle to reflect the light emitted by a small light bulb and then emit it along a straight line.