Physics Help Forum Cast shadow from waterdroplets on a glass window

 Light and Optics Light and Optics Physics Help Forum

 Jan 9th 2018, 02:48 PM #1 Junior Member   Join Date: Jan 2018 Posts: 3 Cast shadow from waterdroplets on a glass window I have query on what is the underlyng principle of Physics behind my observation of a "Shadow created when light passes through a waterdroplets on a glass window" Thanks in advance for your answers.
 Jan 9th 2018, 07:02 PM #2 Senior Member   Join Date: Aug 2010 Posts: 264 Water droplets are partially transparent- some of the light striking them passes through, some is absorbed or reflected. The "shadow" will be grey rather than black because of the light passed through.
 Jan 9th 2018, 07:56 PM #3 Senior Member   Join Date: Apr 2017 Posts: 154 A shadow is usually formed when a solid object blocks the light ... But in the case of a water drop the light goes through , but because the surface everywhere on the drop is curved , it will go in many directions except strait through in a strait line ... hence the shadow.
 Jan 9th 2018, 09:08 PM #4 Junior Member   Join Date: Jan 2018 Posts: 3 Is there a way to measure or an equation that governs the shadow created by droplets in glass window? Thanks guys for the answers.
Jan 10th 2018, 12:22 AM   #5
Senior Member

Join Date: Apr 2017
Posts: 154
 Originally Posted by Switchlink2000 Is there a way to measure or an equation that governs the shadow created by droplets in glass window? Thanks guys for the answers.
No equation is needed ...

We know for sure everywhere on the surface of the drop is curved , so the light that passes through the drop is refracted at many different angles ,like a very complex lens.
So if the surface is relatively far from the window , perhaps a meter, then we know the shadow cast on it will be perfectly black ....

Except for the light it receives randomly from other drops scattering small amounts of light , or scattered light , bouncing off walls etc.

The above is only true if the light source is either a perfect point source or perfectly parallel ....

If using the sun , the shadow will never be perfectly black , many factors involved ... size of drop ...distance of screen from window .

 Jan 13th 2018, 04:38 AM #6 Junior Member   Join Date: Jan 2018 Posts: 3 Is there a way to measure the "shadow" that will be created? I want to find out if there is a direct relationship to a blurred image caused by water droplets from an observers POV. Thanks again.
 Jan 13th 2018, 06:52 PM #7 Senior Member   Join Date: Apr 2017 Posts: 154 can you tell me how far the screen is from the glass with the water drop .. what is the light source ?

 Tags cast, glass, shadow, waterdroplets, window

 Thread Tools Display Modes Linear Mode

 Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post RubberDucky Advanced Thermodynamics 6 Mar 21st 2017 04:44 PM Lindapot Thermodynamics and Fluid Mechanics 4 Nov 9th 2016 08:20 AM Willy99 Advanced Optics 1 Aug 9th 2010 09:35 PM jenshu Light and Optics 1 Feb 22nd 2010 05:59 AM werehk Light and Optics 2 Dec 14th 2008 09:17 AM