Some more applications of photoelectricity for you

As I have mentioned in my previous blog that I will deliver some more applications,so let's get started:-

• Reproduction of sound in cinema films:sound is recorded as variations in light intensity along the pictures in a cinema film.Now what is done is that the film with recorded sound is made to pass between an exciter lamp of constant intensity and photoelectric cell.So,because of the varying intensity of recordings we get light from the exciter lamp falling on the cathode of the photoelectric cell with varying intensities.This light of varying intensities causes electronic emission of varying currents and this is amplified and fed into a loud speaker and sound is reproduced.
• Light meters and exposure meters-we know that a sufficiently intense light with the right frequency that is threshold frequency can cause photoelectric emission and this concept is used in camera.This thing is observed on a suitable scale and correct exposure on tha camera can be set manually or automatically.
  
• Solar batteries-I know many of you have heard of solar batteries,and you will find that many of this are operational in chinese mobile handset that are widely sold all over the world.The batteries generally contain photovoltaic cells that convert solar radiations into electrical emf.

                                                             

• Automatic street lights- If you have read my previous blogs there I have mentioned the concept of relay  which is used here but still if you want to know more about it then go to this link( http://en.wikipedia.org/wiki/Relay).Here what is done is that photocells with connected relays are kept facing the sky and the moment sky is overcast with dense clouds and when night falls,the light is cut off and it operates the on switch of the relay which causes street lighting to be switched on automatically.
• Thickness control of paper -what is done here is that a photocell is placed below the roll of paper in which we want to determine thickness and the source of light is placed above.Now if the thickness of the paper is not upto the pre-set values then more light will enter the photocell and it will eventually manipulate the relay to operate the yes switch which will in turn instruct the machine to reject the paper.

Now,you can imagine what Einstein has done for us,so it's upto you to bring your wild ideas into operation and hence extend this list of applications.So,just operate the Yes switch of relay in your brain and  by the way your comments  are welcome and thanks for reading it!!!