# Tag Info

## New answers tagged diffraction

1

The off-axis intensity is not sero, it is simply quite low. This article on the Wolfram web site shows the 2D diffraction pattern from the sort of aperture you describe along with the equation for calculating the intensity: $$I = 16C^2a^2b^2\left(\frac{\sin(\theta_xka)}{\theta_xka}\right)^2\left(\frac{\sin(\theta_yka)}{\theta_yka}\right)^2$$ where the ...

0

The issue here isn't quantum mechanics but whether a description using only local fields is possible. Quantum mechanics is essential as you are considering an interference phenomenon. The alternative would be to consder a charged classical field that corresponds to the electrons in a superposition of the two paths, but then you are simply considering the ...

0

This is what the author of http://arxiv.org/abs/1407.4826 seems to imply. I have no idea if this is correct or not, sorry.

0

To simplify the problem, I will use a source of light with only three different wavelengths. One for red, one for green and one for blue. If I pass "this light" through a red filter, only the red light will pass, and the green and blue components will be blocked. If I then put the green and/or blue filter on top of the red filter, no light will pass ...

0

You say: obviously, the diffraction from two atoms really tells you literally nothing but that isn't true. Two atoms will give you a Young's slits type diffraction pattern and you could measure the fringe spacing to determine how far apart the two atoms are. In practice you'd run into some severe experimental difficulties! Still, in principle you'd ...

0

While David Hamman's answer is correct, I wanted to expand a little bit on his answer: When you use a CRT, you are looking at emitted light. In the case of emission, there is no "absolute" white - something will only look gray in comparison to something else with the same color ratio but brighter. When you turn up the brightness on your monitor, white is ...

0

This is an interesting question, but I think it concerns physiology rather than physics. As I'm a physiologist, I'll attempt an answer. Our color vision begins with the different spectral sensitivities of our cone (photopic/bright light) receptors. These are often called red, green and blue cones, but in fact each is sensitive to an extent to a side range ...

41

What you are seeing at a distance is not black. It is a darkish shade of gray, RGB gray 85,85,85. The reason you aren't seeing "white" is because each of those three rectangles has an HSV value of only 33% and you are seeing that merged square against a white background. That merged square will appear to be whitish if you make the background black rather ...

3

There are a lot of good answers already here, but I think I'll add a few pictures that show the ways I have to force myself to think to keep track of the differences between light waves and light rays when thinking about diffraction patterns. Above we have some light coming through the center of the slit. If we draw it like this it seems to make sense with ...

28

Why will a blue ray bend lesser than a red ray through a slit of the size a little bigger than the wavelength of the blue ray? Don't think of bending. Think of diffraction like this: if you have a plane wave incident on a slit, then you can think about the space in the slit as being a line of infinitely many point sources that radiate in phase. If you ...

0

Take a plastic ruler and attach it to a table. Press the ruler with your finger down, after move your finger slowly back. The ruler is elastic and moves back in the outgoing position. this is because the ruler is an elastic body. Press again and take the finger away as fast as you can. Now the ruler vibrates. This happens because you put energy into the ...

1

The interference between all the rays emitted from the aperture to a fixed point on the screen can be constructive or destructive, depending on the various path lengths involved (measured in wavelengths). If you change wavelengths, the path lengths (measured in wavelengths) change. What is constructive interference between paths at one wavelength can be ...

1

A wave is a perturbation in a system that propagates. The wavelength is the typical length along which a wave is coherent, which means that what happens at some position affects the wave behaviour in the vicinity if this point at distances of a few wavelengths. The reason for that is that the medium in which the wave propagates has some rigidity and the ...

6

My answer will be quite close to that of PhotonicBoom although a bit more graphical. When it comes to light phenomena, there are different ways to comprehend them: we can use a wave picture (Hyugens-Fresnel), we can use the most modern picture we have (QED) or we can use something a bit more intermediate which is the picture of light rays travelling from ...

4

The answer lies in QED and is quite complicated mathematically. As a simple explanation this is what happens: Photons follow all possible paths from the source to the screen and each path has its own probability amplitude associated with it. Summing up all these paths cancels out most terms in the summation and you end up with your desired final "classical" ...

4

Huygen's principle alone will not answer your question, however the Huygen-Fresnel principle modifies this to include wavelength. It states that every point in an unobstructed beam acts as a secondary source of wavelets with the same wavelength as the primary wave. The amplitude of the optical field at any point is then the superposition of all the wavelets. ...

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