Angle of Incidence and Reflection.

[bestpavan]

Hi,

Can someone please eloborate me why the Angle of Reflection is always same as the Angle of Incidence. I want the explanation at photon and molecular interaction level.

Thanks in advance.

- Pavan.

 

[tiny-tim]

Welcome to PF!

Hi Pavan ! Welcome to PF!

I think it's simply conservation of energy and momentum …

if no energy is lost (ie if the wavelength of each photon stays the same), and if the reaction force is normal to the surface (which it must be if the surface doesn't change shape), then the angles must be the same.

 

[bestpavan]

Hi tiny-tim, Thanks for the Reply!

Actually I am only 50% satisfied still.

What is it that the photon is interacting with?

Lets say, I shine some light on a pool of water, what is it that is causing the "normal reaction"?

Is the photon bouncing off the nucleus of Hydrogen and Oxygen atoms? If so, how?

- Pavan.

 

[Jame]

The actual mechanism of the interaction between the photon and the atoms in the material is a very complicated process as far as I know, but I can try to give you my amateur explanation.

When the EM wave reaches the reflecting surface it slightly enters the material and interacts with the atoms. The atoms are bound together and electrically charged, which means that they are effectively working as balls connected by springs. The light wave makes the balls move, but they are retained by their bindings and therefore they start to oscillate. Oscillating charges means electromagnetic fields, which naturally has to be the opposite of their cause. A new EM wave is generated and sent in all directions but those who go back into the material will eventually be absorbed.

This process depends on the structure of the atoms which is the reason why some materials almost let light pass right through it, some reflect most of it, and most do both.

 

[bestpavan]

Hi Jame, Thanks for your reply.

Can anyone explain how prapogation of light through transparent objects work?

How can most of the photons travel so perfectly aligned through a solid object?

My another question is regarding Polarization. How do polarizors work?

- Pavan.

 

[Andy Resnick]

Hi,

Can someone please eloborate me why the Angle of Reflection is always same as the Angle of Incidence. I want the explanation at photon and molecular interaction level.

Thanks in advance.

- Pavan.

It isn't, in general- only for specular reflection.

 

[bestpavan]

Hi Andy,

Could you please kindly answer the other questions in my earlier posts!

Thanks in advance.

- Pavan.

 

[Andy Resnick]

I would be happy to help you understand any points you are not sure about- but I can't help you unless I have a better idea of what you understand already.

 

[bestpavan]

Hi Andy,

Thanks for your commitment to help others!

I have a decently good idea about physics. However, my understanding is limited to the "Principles" of it, and not the exact reason behind those principles.

To start with, could you please tell me what an Electro-Magnetic wave exactly is? and how it is generated from an atom? And how does that wave prapogate in vacuum?

Thanks in advance.

 

[Andy Resnick]

I'm not sure what electromagentic waves *are*, in all honesty. I know there are several ways of describing electromagnetic phenomena including a continuous field theory (waves), a quantized field theory (photons), or as rays (geometical optics).

Propogating EM waves can be generated in a number of ways- including bound state transitions of an atom. In the wave picture, the wave propogates by itself:there need be no 'medium' in which the wave propogates.

Does this help?