LENZ'S LAW

A.C.GENERATOR WORKING

MNEMONICS TO MEMORISE FORMULAE

H = Vit                         

B = μ0nI/2a

I0 = nIL

N = nAL

F = VeB

F = eE

B = μnI

Ʈ = nABI sinθ

I = Cθ / BAn

I = nAeVd   

J = enVd

IL = -nAeLVd

F = BIL Sinθ 

μl = hen / 4лm

μl = he / 4лm , when n = 1

μl = evr/2

θ/I = BAN / C 

θ/V = BAN / GC

Ø= BAN cosθ

LI = Ø

L = μ0NNA / L

M = μ0N1N2A / L

ß = λD/ d

I = K tanθ

JA  = I

Chemical Equivalent = RAM/val

dB = IdL sinθ / r2

ES/EP = NS/NP = IP/IS

Ø/δ = 2л/λ

b/a = (L+1)/n

B=µI/2лa

Thermo Electric Series

Bi, Ni, Pd, Pt, Cu, Mn, Hg,

Pb, Sn, Au, Ag, Zn, Cd, Fe, Sb

VI = P

Silver = 10%

Gold = 5%

Red = 2%

Brown = 1％

M = IA

δ= xd /D

r2n = λRn

Sinθ = mλN

Sλ = θ/LC

e/m = v/Br

λmin = hC/ eV

E = eV

V = EL

V = Ed

C = ε0A / d ;  C’ = ε0εrA/d

E = 1/2 CV2

E =1/2 LI02

R = mL / nAe2Ʈ

α= IC/ IE

q = ne

q = LAne

e = LBv

(θc+ θi) /2 = θn

V = Er

q = It

ρ= RA/L

W = Vq

V = IR 

e/m = v/Br

r = (E-V) R/V

TOTAL INTERNAL REFLECTION

Sin i / Sin r = (BC/AC) / (AD/AC) 

Sin i / Sin r = BC/AD

Sin i / Sin r = Cm.t /Ca.t = Cm / Ca

    AD<AC                        AD=AC                                AD>AC

1.(AD/AC) < 1                 (AD/AC) = 1                           (AD/AC) > 1

2.Sin r < 1                      Sin r = 1                                Sin r > 1

3.r < Sin-1(1)                   r = Sin-1(1)                          r > Sin-1(1)

4.r < 900                          r = 900                                r > 900

5.i < C (critical angle)         i = C                                  i > C

6.Refracted wavefront      Refracted wavefront              Refracted wavefront

  is possible                  is just possible,the               is not possible

                                   refracted ray grazes

                                   the surface of separation

INTERFERENCE IN THIN FILM - DERIVATION

Hints and formulae :

* from triangle 1 , BM / BE = sin i

               

               BM = BE sin i  ----------------> 1

* According to Snell’s Law , µ = sin i / sin r ,

                        

               Sin i = µ sin r  ----------------> 2 

* from triangle 2 , BL / BD = sin r  ( BL = 1/2 BE )

                   1/2 BE / BD = sin r 

                       

               BE = 2 BD sin r  ---------------> 3 

* from triangle 2 , DL / BD = cos r  (DL = t)

                t / BD = cos r   ----------------> 4

Interference due to the Reflected Beam

Derivations : 

from E , draw a normal EM to BC. The path difference between the waves BC and EF ,

δ = (BD+DE)M - (BM)A

                       Since, µ = λM / λA , i.e., λM = µ λA

δ = µ(BD+DE)A - (BM)A      (from the diagram,BD=DE)

So, δ = µ(2BD) - (BM)

                       From equation 1, BM = BE sin i

So, δ = 2µBD - BE sin i

                       From equation 2, Sin i = µ sin r

So, δ = 2µBD - BE(µ sinr)

                       From equation3, BE = 2 BD sin r 

So, δ = 2µBD - 2µBDsin2r

δ = 2µBD (1-sin2r)   :  δ = 2µBD cos2r

                    From equation 4, t / BD = cos r 

δ = 2µBD cosr . cosr

δ = 2µBD(t/BD).cosr

δ = 2µt cosr

 * Any light ray undergoing Reflection at the surface of a Denser medium will suffer a Phase change of Π or an additional Path difference of λ/2.

 * At B due to reflection, there is an additional Path difference λ/2

So the effective path difference is , δ =2µt cosr + λ/2

For constructive Interference ,δ = nλ

 i.e., δ =2µt cosr + λ/2 = nλ (or) 2µt cosr + λ/2 = nλ

So,  2µt cosr = λ/2 (2n-1)

For destructive Interference , δ =(2n+1)λ/2

 i.e., δ =2µt cosr + λ/2 = (2n+1)λ/2 

                  

   (or)

         2µt cosr + λ/2 = (2n+1)λ/2 

  

So,  2µt cosr = nλ

      If light is incident Normally ,i = 0 and hence r = 0 ,

therefore the condition for Bright fringe is ,

             2µt = (2n-1)λ/2

And the condition for Dark fringe is ,

             2µt = nλ

HOW TO GET CENTUM IN PHYSICS

* DO NOT WRITE IN BALL POINT PENS WRITE THE EXAM ONLY IN GEL/INK/STICK PENS.
* FOLLOW THE NEATNESS TILL THE LAST PAPER / PAGE. MORE THAN HANDWRITING NEATNESS IS ESSENTIAL.
* AVOID STRIKINGS,SCRIBBLINGS,WRITING IN A ZIGZAG FASHION AND AVOID OVERWRITINGS TOO.
* LEAVE SPACE BETWEEN EACH WORD AND EACH SENTENCE.
* IF YOU HAVE TO STRIKE ANY WORDS OR ANY SENTENCES STRIKE USING PENCIL.
* DRAW THE DIAGRAMS WHEREVER NECESSARY EVEN FOR SOME THREE MARKS QUESTIONS DIAGRAM IS NECESSARY AS GUIDED BY THE SUBJECT TEACHER.
* WHILE DRAWING DIAGRAMS PUT DOTTED LINES WHEREVER REQUIRED,USE ARROW MARKS,ANGLES,COMPONENTS,SUFFIXES,PREFIXES WHEREVER NECESSARY,LABEL THE PARTS AT THE APPROPRIATE PLACES,ETC.,
* FIRST ATTEND THE KNOWN OR EASY SECTIONS FOR YOU TO BE TENSION FREE OR IT IS BETTER TO ATTEND 10 MARKS FIRST,LATER 5 MARKS,3 MARKS AND AT LAST 1 MARK.
* PUT THE CORRECT QUESTION NUMBER ,WHICH SECTION,ROMAN LETTERS, EVEN THE OPTIONS FOR COMPULSARY PROBLEMS ETC.,
* FOR ONE MARK ATTEND IN THE PATTERN GIVEN HERE THAT IS WRITE Q.NO THEN OPTION AND THEN THE ANSWER (I THINK YOU HAVE UNDERSTOOD).
* PLEASE GIVE IMPORTANCE TO PROBLEMS SO AS TO GET FULL MARKS AND THE PROBLEM PATTERN MUST BE , GIVEN DATA,FORMULA(E),SOLUTION AND THEN THE RESULT WITH UNITS.WHILE WRITING GIVEN DATAS WRITE THE QUANTITIES WITH UNITS .
* DEFINITIONS MUST NOT BE WRITTEN ON YOUR OWN IT HAS TO BE WRITTEN AS WHAT GIVEN IN THE TEXT BOOK.
* TO ATTEND THE TYPE OF 3 MARKS QUESTIONS GO THROUGH THE 2ND PAGE OF VIVEGSENA (http://vivegsena.weebly.com) BY CLICKING DECEMBER 2011 IN THIS PAGE AND AFTER OPENING OF VIVEGSENA HOME VIEW 2ND PAGE.
* MOSTLY FOR 5 MARK PROBLEMS USE LOGARITHMS.
* FOR ONE MARK READ BOTH FROM PTA BOOK AND TEXT BOOK BACK FROM THE BEGINNING OF THE SCHOOL DAYS ITSELF.
* TRY TO FINISH THE PAPER BEFORE 15 MINUTES FOR CHECKING OR WRITING ANY MISSED ANSWERS.(GO THOROUH FULLY AS SAID ABOVE IN THAT SITE IN 2ND PAGE).
*IF YOU FOLLOW THESE SURELY YOU CAN SCORE CENTUMS BUT MAKE SURE THAT YOU ARE THOROUGH WITH EVERY PAGE OF THE BOOK BY UNDERSTANDING THE CONCEPTS WELL.

G M COUNTER

USE: To measure the intensity of the Radioactive radiations.

PRINCIPLE: Ionisation produced in the gas by nuclear radiations .

CONSTRUCTION: 
* A metal tube with glass envelope (C) act as cathode.
                                  
*A fine tungsten wire (W) along the axis of the tube, act as anode.
                                 
* GM tube insulated from the wire is filled with an inert gas like argon at a low pressure.
                                  
* The radiations enter through a window (E) made of thin mica sheet.



*About 1000 volt is applied through a high resistance R (100 M ohm)
                                    

WORKING:           

* Due to primary ionisations few ions produced are  accelerated by high potential difference .  
                                   
* These ions/electrons cause further ionisation and due to collisions, avalanche of electrons are produced.
                                    
* These electrons reaching the anode produces a current pulse.
                                   
* A high potential difference developed across R is amplified and operates an electronic counter. 


* The counts in the counter is directly proportional to the Intensity of Ionising radiations.


* Ionisation of the gas does not depend on type of Incident radiations.


* Wilson's Cloud Chamber ,a particle detector records the visual observations of the tracks of charged particles.