Galilean Telescope

In designing a Galilean telescope , the main points which should be kept under consideration, are :

1-A concave lens forms inverted and magnified image if the object for the concave lens is virtual and its distance is smaller than the twice of the magnitude of the focal length and grater or equal to the focal length.

2-The final image which is now going to be erect, should be at distance 25cm or greater I and it should be also virtual.

3- Where we require shorter telescope, Galilean is better option. Binoculars use this one.

Simple. Microscope

Irodove Problems ..useful for JEE

Capacitor ++

Charging and discharging of capacitors:

Gauss Law related problems :

GYThe In any region if the volume charge density is not constant then it will be wrong to multiply total volume with density at only one point.In such cases small volume is properly selected and this small volume is multiplied by the charge density in this small region to get charge in this region to get charge of the small region. This small charge is now integrated to get charge of some large portion. Following example deals with such one case where charge density is varying with radial distance from certain point.

Solution :

इस problem में सबसे important है volume element select करना।  यह भी ध्यान रखना चाहिए की density constant न होने पर charge density को कुल volume में multiply नहीं कर देना चाहिए। 
                                                                                           

• One of very important concepts in regard to the Gauss Law is that in a region with uniform electric field, any small or large portion will be free of net charge. In other words any closed surface constructed in such region will be associated with net zero electric flux because the number of electric field lines entering the closed surface will be same as the number of field lines leaving other part of the surface.
• Gauss Law will have  validity only if the electric field of point charge vary as  inverse square of the  distance from the charge. किसी ने एक बार पूछा  कि  इलेक्ट्रिक dipoles की फील्ड तो  distance cube के inversely proportional होती है ,तब क्या dipoles  के लिए यह  Gauss law valid नहीं होगा ? For a moment I too was forced to think but quickly it clicked correctly in my mind that dipole is not a point charge so it is immaterial for the validity of the Gauss Law  how the field of dipole vary with distance .

# Let a uniform electric field E exist in a region where a Gaussian surface  which is in the form of a frustum of a cone  is constructed . At the two ends , radii  are b and 2b respectively. The field is parallel  to the axis of the conical frustum. How can we get the electric flux through the lateral surface of the conical region? 

Problem on Electrical circuits 31 May 15

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