photodiode sensor

i want to make a sensor using photodiodes. here photodiodes are connecting parallel and to each photodiode i have to put a load resistance. how can we calculate the value of photo diode? on what basis we can design the load resistance value. i am applying a voltage of 2.5 volt . Is there any method for finding the load resistance value of a photo diode ?

Asked Indira

 

 

Nature of Electromagnetic Waves

When we represent the frequency, amplitude, and wavelength of any electromagnetic radiation on a graph we see a wave like in water. Is this just a geometric representation or do the “packet” aspects of these waves actually move physically like the mathematical representation.

Asked Jack Cassidy

Hope that the following videos explain the concept better

English: Electromagnetic waves can be imagined...

English: Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. This diagram shows a plane linearly polarized wave propagating from left to right. The electric field is in a vertical plane and the magnetic field in a horizontal plane. http://weelookang.blogspot.com/2011/10/ejs-open-source-propagation-of.html (Photo credit: Wikipedia)

 

Air Pressure Again

A metal box, opened on the top, in put on the ground, then it’s closed welding a metal surface on it, in order to obtain a parallelepiped full of air. Suppose that the box walls are so strong that they would be perfectly resistant to the outside air pressure even if the box was empty. Then the air inside the box isn’t subjected to any influence by the external air pressure. In other words, standing inside the box there is no way to understand if outside there is air or empty space. Now, according to Stevin’s law, the pressure on the bottom surface inside the box should be equal to dgh, where h is the box height, much less than the air pressure outside! But actually the internal pressure is the same as the external pressure. I can’t find the mistake. Moreover i can’t understand how the pressure p in the gas law pV=nRT is involved in all that. thank you.

Asked Alessandro Morelli
Answer