In principle, light should be straight, but because the fine substances in the air refract the light, causing it to deviate from the angle and diverge, so it looks like a divergent figure of eight< /p>
Also, the function of the flashlight is weak and easy to be refracted. If the energy of a laser is strong, the refraction will be small and it will look like a straight line. In fact, there are some changes, but it cannot be observed. Ideal A straight line is a true straight line that is emitted in a vacuum state without any impurities in the space