How can light be considered a particle and not a wave?

Question

I'm currently 15 and haven't taken any physics classes yet, but I have an idea of what light is thought to be from reading some books.. I read a book that said that Einstein has a theory that light is a particle aswell as a wave.. but if it was a particle. If i shawn a light onto a material that light couldn't pass through that had a.. let's say 2 inch hole in it.. and onto a wall 2 metres away. If light was a particle and not a wave.. on the wall wouldn't we just see the 2 inch diametre circle of light?

I'm sorry it's quite hard to explain..

Answer 1

yogesh is incorrect. Photons do not have mass.

Photons are not particles. They are a form of energy which can take on some of the characteristics of a physical particle. Photons have no mass but they have momentum proportional to it's frequency. Photons are electrically neutral and as such are not affected by magnetic or electrical fields.

Light is a type of electromagnetic energy or radiation. Light is in a constant state of fluctuating electrical and magnetic energy. The electrical field will be at maximum when the magnetic field is at minimum. The electrical field will be at minimum when the magnetic field is at maximum etc. These properties are defined in terms of wavelength, frequency, and speed of propegation. Photons may be slowed by travelling through a medium such as glass or water and photons may be accellerated but light never loses energy. After light gets past the medium it returns to normal speed. It is never slowed by friction like other particles or bodies will mass therefore it can not be a particle.

It was Einstein who changed the understanding of how light waves seem to bend by gravity from the old Newtonian views. Today, we think not in terms of vector forces when describing the Universe but in terms of spacetime. The consequences of the 'shape' of the Universe.

Let's use an example of a body with a large mass. It does not have to be a black hole although that would be an extreme example which seems to come to most peoples mind the quickest. The mass of the object exerts a large gravitational pull not only on the objects around it but also on the space around it. Thus, it follows that the space around this object is already curved. Light travelling along this space would simply follow the curvature which is already in existence. Gravity is not bending the light. The light is simply following the curvature of spacetime which is already bent.

Answer 2

You're exactly right, if light was strictly a particle you would see the 2 inch diameter circle of light on the opposite wall. However light exists as both particles and waves.

Here's some background for you. For a long time the definition of light was either a particle or a wave. There were 2 different factions that held that light was either one or the other, but couldn't possibly exist as both.

Then in the late 19th / early 20th centuries they figured out that light exists as both a particle and a wave. This is what's called "wave-particle duality".

Light was commonly considered a particle by what's called the photoelectric effect, where when light struck certain metals it would produce a shower of electrons that were knocked off the metal plate onto a sensor. Now to do that light would have to be a particle knocking the electrons off of the metal plate like a cue ball striking a cluster of billiard balls.

However the flip side is that when you shine light through 2 slits at the same time known as the "double slit experiment". You will notice a series of light and dark stripes on the screen it shines on. Now if it was strictly particles you would see only 2 light stripes as the particles passed through the 2 slits only and the rest of the particles in the beam were absorbed by the material that formed the slits. However they saw multiple bands of light on the screen beyond the slits.

Now the only way that can happen is if light was a wave and it generated the multiple stripes by both diffraction (light bending around an object) as well as "constructive/destructive interference".

Now constructive interpherance is where there are 2 waves that have the same amplitude (wave height) and are in perfect phase (0 degree phase difference or perfectly sync'd) they'll increase the amplitude and make the stripe seem even brighter.

Destructive interpherence is the same principle except the two waves are 180 degrees out of phase. The peak of one wave occurs at the same time as the trough of the second wave occurs in the same cycle. This will cancel out the amplitude and make it equal to 0 which will result in a dark stripe that you'll see.

Now Einstein and several other physicists through their mathematics were able to prove that wave-particle duality did indeed exist for light, which drew the debate to a close.

I realize this is a long explanation, but I hope it helps clear up any confusion you may have had. You're on the right track, and have a good grasp of the concept.

Answer 3

Light is both a particle as well as wave.

It has photon particles with very little weight. It has been proved in lab that light ray bends under influence of gravity, thus it has mass.

It is also a wave that is why a light through a 2" hole will look bigger on the wall where it is projected. However, laser is a different thing. A laser beam through a 2" hole will show diameter of maximum 2" even at a long distance. This is because in laser, the light energy is concentrated by filtering it and cutting down wave amplitudes. Light is an electro-magnetic wave with electric and magnetic waves at perpendicular to each other.

It is difficult to comprehend, but light has both wave and with mass, just like water waves. Since photon particles are very small, they can pass through paper, but not through wood or wall, which will absorb its wave energy.

Many things in the science works on some 'understanding' which no body knows. For example, no one understands electricity or how it travels, but still we run electric devices.

Sir Isaac Newton declared in 17th century that light is a wave. Opponents asked then how it can travel in space, in a vacuum? He theorized that inter-planetary space is filled with a material called ether. He added that ehter is so light so that it will not slow down the rotation of planets! He also said that sound is the max speed any object can travel!

Answer 4

The simplest analogy I've ever seen deals with a stone tossed into a pond of still water. Waves radiate out from where the stone landed, but the waves themselves are made up of individual water molecules (..particles..)

Answer 5

The modern theory of light is that it is both a particle and a wave.

Answer 6

did you know that light exerts force just like you exert force with your hand. only particles exert force. waves only provide energy & it is the particles that carry the force forward. using this line of thinking light can be considered to be a particle(although the force exerted by light is of a very small magnitude, in piconewtons i.e 10^ -12 N)

Answer 7

easy has twin nature i.e. on occasion it fairly is seen as wave & it sluggish as particle. Wave nature lead Huygen to create wave optics wherein diverse phenomenons are studied like as Intereference and Diffraction phenomenon. mutually because it replaced into particle nature which bring about invention of mirrors, lenses and telescopes and defined specific phenomenon like Mirage and dealing of optical fibers.

Answer 8

Welcome the the world of quantum uncertainty!
Light exhibits the characteristics of both

At high energies its behavior is 'particle-like`,
and at lower energies, 'wave -like`.
(Interference and measurable impact.)
Lights course bends in a gravitational field.

The 'dual nature` answer is the only one that works...so far.

Answer 9

it's actually both. it act as if its both a wave and a partiacle.