Chapter #10 :Geometrical Optics : Short Q/A / C.R.Q's

Q.Why do thick lenses possess chromatic and spherical aberrations? Suggest remedies for the rectification of these defects.
Ans.Chromatic aberration occurs because lenses have a different refractive index for different wavelengths of light (the dispersion of the lens) and spherical aberration is an optical effect observed in an optical device that occurs due to the increased refraction of light rays when they strike a lens or a reflection of light rays when they strike a mirror near its edge, in comparison with those that strike nearer the centre.
Chromatic aberration was reduced by increasing the focal length of the lens where possible.

Q. Does the chromatic aberration takes plane in mirror?
Ans. In optics, chromatic aberration (chromatic distortion) is a type of distortion in which there is a failure of a lens to focus all colors to the same convergence point. It occurs because lenses have a different refractive index for different wavelengths of light (the dispersion of the lens).But A/c to law of reflection” The angle of incidence is always equal to law of refraction”. So there is no chance of chromatic aberration in mirror

COMMON COLLECTOR CONFIGURATION OF A TRANSISTOR

COMMON COLLECTOR CONNECTION

In  this  configuration  the  input  is  applied  between the  base  and  the  collector and  the  output  is  taken  from  the  collector  and  the  emitter.  Here  the  collector  is common to both the input and the output circuits as shown in Fig.

Common Collector Transistor Circuit

In  common  collector  configuration  the  input  current  is  the  base current  IB  and  the output current is the emitter current IE. The ratio of change in emitter current to the  change in the base current is called current amplification factor.

It is represented by

COMMON COLLECTOR CIRCUIT

A test  circuit  for determining the  static characteristic  of an NPN transistor is shown in Fig. In this circuit the collector is common to both the input and the output circuits.   To   measure   the   base   and   the   emitter   currents,   milli   ammeters   are connected in series with the base and the emitter circuits. Voltmeters are connected   across the input an…