# Question about behaviour of light

## Recommended Posts

The sun shines through the window and casts a shadow of a black pipe vertically onto the ground. The resulting shadow has different colors on different sides. Relative to the sun on the left side, the edge is orange-ish in color, and the right edge is blue-ish in color.

At certain places, the edges have no orange-ish nor blue-ish colorations, particularly the part of the shadow closer to me.

Furthermore, at different angles of shadow cast from the sun, the colored edges changes in sharpness, going from blurry to a sharp "clean" that seems even brighter than the actual, adjacent light on the ground.

I might have an idea why the edges change in sharpness, but I am completely oblivious to why the edges are different colored. Any the answer?

Edited by Vay
##### Share on other sites

I can't answer in details, but you can check "diffraction" or "refraction". Both of these are wavelength dependent, so it would effect different colors differently.

##### Share on other sites

I can't answer in details, but you can check "diffraction" or "refraction". Both of these are wavelength dependent, so it would effect different colors differently.

Thanks I am not up to that in my physics class yet, still doing mechanical motions. But I will definitely refer back to this problem after I do study it. The resources online doesn't really help too much, they go into the equations and what-not.

Although I realized that my diffraction scenario would be just a pipe blocking the sunlight, such that the light will shine completely on both sides of the pipe. I have no clue what such diffraction pattern would look like.

I also forgot to add that the room I was in had fluorescent bulbs on, so that might add some implications.

Edited by Vay
##### Share on other sites

Do you have a picture? It's hard to imagine how the pipe can diffract considering that the pipe is way bigger than the wavelength of light.

##### Share on other sites

Do you have a picture? It's hard to imagine how the pipe can diffract considering that the pipe is way bigger than the wavelength of light.

I saw it in class, plus I don't have a USB for my flip-phone to transfer pictures, but I will draw it and label it, then upload it here.

Edited by Vay
##### Share on other sites

It's difficult to envisage this without seeing it. A photograph of the shadow, window and pipe would help.

What colour is the ground? Have you tried placing a piece of plain white paper on the ground to eliminate the colour of the ground affecting what you see?

Secondly are the colours you see within the shadow due to light coming from somewhere else? Light refracted in the window glass perhaps, another source reflecting light within the room or outside the window?

Thirdly, are the colours very near the edge of the shadow or more diffuse across a wider area of the shadow?

Edited by Griffon
##### Share on other sites

I tried doing it on my porch but nothing of that happened. Will try to post a photo. Also, how did you managed to see the blueish shadow? It's...just too strange because this becomes more like scattering of light than diffraction.

##### Share on other sites

every point on the floor receives different coloured light refracted from different points of the glass,however at the edge of the shadow not all colours can reach those points from any point on the glass.

##### Share on other sites

I saw it in class, plus I don't have a USB for my flip-phone to transfer pictures, but I will draw it and label it, then upload it here.

Hi Vay,

I have seen similar effects so it would be interesting to see the pictures.

##### Share on other sites

I have attached a sketch of the scene I remembered, so it is not an 100% accurate representation. The circle on the right is a close-up of the shadow of the pipe. I can't get a picture because I am on spring break.

The blue and orange streaks are brighter than the surrounding light when the streaks are concentrated onto a thinner line, which makes sense. At different shadow angles, the streaks disperse and are not as bright anymore. The fluorescent bulbs on the ceiling are on.

Edited by Vay

## Create an account

Register a new account