Light is a form of energy that helps us see.
光是一种能量，它帮助我们看清世界。
In the same material, light always travels in a straight line.
在同一种物质中，光总是沿直线传播。
This is why we can see things clearly in front of us.
这就是为什么我们能清楚地看到前面的物体。
But when light meets an object, it cannot pass through solid things.
但是当光遇到物体时，它无法穿过不透明的物体。
This is why shadows are formed.
这就是影子形成的原因。
A shadow appears on the opposite side of the light source.
影子出现在光源的另一侧。
The size and shape of a shadow depend on the object blocking the light.
影子的大小和形状取决于挡住光的物体。
If the object is close to the light, the shadow is bigger.
如果物体靠近光源，影子会更大。
If the object is far from the light, the shadow is smaller.
如果物体远离光源，影子会变小。
Light can change direction when it hits a mirror.
当光线碰到镜子时，它的方向会改变。
A mirror reflects light, making it bounce back.
镜子会反射光线，让光线反弹回来。
That’s why we can see our faces in a mirror.
这就是为什么我们能在镜子里看到自己的脸。
Light can also bend when it moves from one material to another.
当光从一种物质进入另一种物质时，它可能会发生弯曲。
This is called refraction.
这种现象叫做折射。
For example, when you put a straw in a glass of water, it looks bent.
比如，当你把吸管放进水里，它看起来像是弯曲的。
That happens because light changes speed in water.
这是因为光在水中传播的速度不同于空气中。
Without light, we would not be able to see anything.
如果没有光，我们就什么都看不到。
Now you know that light travels in a straight line, forms shadows, and can be reflected by mirrors!
现在你知道光是直线传播的，会形成影子，还能被镜子反射了！
