Why do scientists describe light as both particle-like and wave-like?

Answer 1

The reason that light could be described in these two different ways is because it can clearly be demonstrated to behave like one or the other, depending on the experiment we perform. Curious? Let's look. If light is a particle, when we shine it through a small hole, it will pretty much go "straight through" and make a "spot" on a wall behind that hole. It does. Simple and easy. We'll have to stretch a bit to see the next example, so let's jump on it. Picture a swimming pool with a wall dividing it in half. The wall is solid, and has a soccer-ball sized hole in it in the middle of that wall at the surface of the water. We've got the surface of the water calm. See the picture? Now we take a bucket and kneel down near the edge of the pool in the middle of one side. We hold the bucket with both hands, placing them on the rim of the bucket, and on opposite sides. We gently "set" the bucket on the calm surface, and then start pushing it down gently and then pulling it up gently. We're created a wave generator. We don't have to push too hard or too deep, but we do need to do at least a cycle per second or so to keep things "crisp" and make good waves. We keep doing it. See the waves going out from the bucket? They're heading to the wall that divides the pool. At the wall, the waves are reflected, but at the hole in the wall, the wave goes through. On the other side of the wall, the wave moves out from the hole in the same way it moves out from the bucket that created the waves. See the waves moving out from the hole? It's a wave, and it moves out in all directions from the hole, even along the wall. Now add a second hole a little ways away from the first one. See it? Two sets of waves are now appearing on the other side of the wall, while only the bucket is used to generate both. See what's coming? The two holes in the wall act as (two) wave generators for the other side of the pool away from the bucket. Waves are radiating from each hole and moving out in all directions. See them? Now for the kicker. The two waves on that other side of the wall are going to interact. There will be places where crests meet crests and troughs meet troughs and the waves will add. Particles won't act like this, and you can see we're going to look at the other instance where crests meet troughs because the waves act to "cancel each other out" and the water will be calm. The areas of calm will be clearly visible and form lines called nodal lines. If light does this, then light could be demonstrated to be a wave. Ooo, snap! It does! Particle-wave duality is a fundamental tenant of quantum mechanics. Light can be demostrated to be one or the other, depending on the experiment we use to discover its nature. Is light a particle, or is it a wave? It might be said to be a "wavicle" by some. Links can be found below for more information.

Answer 2

Light is sometimes described as a wave and sometimes as a particle because light obviously travels as a wave. It is considered a particle because of the photons. A photon is an elementary particle, the quantum of light and all other forms of electromagnetic radiation, and the force carrier for the electromagnetic force. So therefore, it is a particle and that is why light is considered both a wave and a particle.

Answer 3

Lots of experiments have shown that light has both particle and wave properties, so scientists have accepted the fact that it has both. The same happens with particles like electrons or protons - they, too, have both particle and wave properties.

Answer 4

B/c in some experiments it behaves as if it is a particle. In other experiments it behaves as if it's a wave, which makes it a quite difficult thing to figure out.