1. The focal length of an equiconvex lens in air is equal to either of its radii of curvature. the refractive index of the material of lens is __________
2. A charge of 4x10^-8C is uniformly distributed over the surface of sphere radius 1cm. another hollow sphere of radius 5cm is concentric with the small sphere. find intensity of electric field at a distance 2cm from centre. [K=9x10^9 MKS] [ans in NC^-1]
3. A light of 4560angstrom and 1mW is made incident on photosensitive surface of Cs. If efficiency of surface is 0.1%, then photoelectric current produces is___________
4.A spherical drop of water has 3x10^-10C charge on its surface. 300 volt electric potential exists on its surface. if 27 such identical drops are combined to form a single drop, calculate electric potential on the surface of new drop._____________

Asked by Dhriti | 24th Oct, 2014, 12:10: PM

Expert Answer:

1.
 
Given Focal length, f = R
Being an equiconvex lens, let R1 = R ,  R2 = - R 
begin mathsize 14px style According space to space lens space makers space formula : space 1 over straight f equals open parentheses straight mu minus 1 close parentheses open parentheses 1 over straight R subscript 1 minus 1 over straight R subscript 2 close parentheses Substituting space the space values space we space get : 1 over straight R equals open parentheses straight mu minus 1 close parentheses open parentheses 1 over straight R plus 1 over straight R close parentheses 1 over straight R equals open parentheses straight mu minus 1 close parentheses 2 over straight R 1 half plus 1 equals straight mu rightwards double arrow space straight mu space equals space 3 over 2 equals 1.5 end style 
The refractive index of the material of lens is 1.5
 
Note: Please ask other questions (each question) as seperate separate queries.

Answered by Jyothi Nair | 25th Oct, 2014, 11:15: AM