An Object is Placed on the Focus of an Equiconvex | Diffraction

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  An object is placed on the focus of an equiconvex lens , How is the image changed if (1) the radius of curvature of the lens is somehow increased slightly ,() the refractive index is somehow increased slightly!1) 1 f #(n$1) % % ↑ , f ↑ & 'bject between focus and pole& mage is virtual and magnied&) n ↑ , f ↓ & 'bject between * and *& mage is real and magnied& +)a) -hen low lying aircraft passes over head, we sometimes notice slightsha.ing of the picture on /0& xplain&-ea. radar signals sent by a ow 2ying aircraft can interfere with the tv signalsreceived by the antenna& As a result tv signals may get distorted&b) n 345 if the two slits are illuminated by two bulbs of same power, will there beinterference! No, because the phase difference between light coming from twoindependent sources continuously change. c) 5tate the conditions for di6raction of light to occur!5i7e of obstacle must be of the same order as of wavelength of incie#dent light&d) -hat is phase di6erence between any two points on the wavefront!8 %&9& of a compound microscope # I) When frequencyincreases, RP increases.Ii) RP doesnt change with change in focal length of objective lens.Iii) When aerture increases, ! increases, so, RP increases. + 1 &5how that width central fringe is twice of secondarymaxima in young:s single slit exp  /wo students are separated by a ; m partition wall in aroom 18 m high& f both light c sin2n sin2n ν θ λ θ  =  and sound waves can bend around obstacles, how is itthat the students are unable tosee each other even though they can converse easily! *or pronounced di6raction e6ect, the si7e of the obstacle should be comparable tothe wavelength of the waves& /he si7e of partition is very large as compared tothe wavelength of light and hence it is not di6racted and the two students cannotsee each other&  /he wavelength of sound waves is of the order of the height of partition& t causessound to di6ract and hence they can converse with each other&  /ir derivation and totally refeected prism& +<)1)/wo narrow slits are illuminated by a single monochromaticsource& =ame the pattern obtained on the screen& 'ne of the slits isnow completely covered& -hat is the name of the pattern nowobtained on the screen! 4raw intensity pattern obtained in the twocases& -hen two narrow slits are illuminated by a single monochromatic source,the pattern obtained on the screen is interference pattern consisting of alternative bright and dar. fringes& -hen one of the cities covered completely nointerference occurs& -hen we obtain is di6raction pattern due to single slit&ntensity pattern in the two cases are shown& Diagram.Interference Diraction  1)  /wo coherent waves superimposedeach other as a result interferencepattern is observed 2) width of all dar. bands are equalas well as bright bands 3) ntensity of all bright bands areequal 4)  conditions for interferencemaximum is a > #n? @#n 5) conditions for interferenceminimum > # (nB1)? @# (nB1) 6) intensity distribution graph 1) 4i6erent wavelets of the samewave superimposed as a resultdi6raction is obtained 2) width of the central band ismaximum 3) intensity of central band ismaximum Cdecreases withincreasing order 4) conditions for di6ractionmaximum is a sin D#(nB1)  5) diffraction minimum a sinD#n 6)  intensity distribution graph+ 1E n 3oung:s double$slit experimentusing monochromatic light of wavelength, the intensity of light at apoint on the screen where pathdi6erence is, is K units& -hat is the intensity of light at a point where pathdi6erence is!()A=5 1E Fet and be the intensity of thetwo light waves& /heir resultantintensities can be obtained asG Where, Phase difference between the two wavesFor monochromatic light waves, Phase difference Since path difference , Phasedifference, Given, λ λ   λ  1 I  I φ   =  Pathdiference π λ  = × λ  =  φ π  = : I K  =  When path difference , Phasedifference, Hence, resultant intensity, Using euation , we canwrite! Hence, the intensity of light at a pointwhere the path di6erence is is units& Q 18 A convex lens of focal length 10 cm is place coaxiall!5 cm a a! from a concave lens of focal length 10 cm. If ano#$ect is place 30 cm in front of the convex lens% &n theposition ' ra the ra! iagram of the &nal image forme#! the com#ine s!stem. Ans)1/ v 1 = 1/f    1  + 1/ u 1 , v 1 = 15cm,1/v 2 = 1/f    2 + 1/u 2 , v 2 (  2#$ (a)  Figure shows a cross%section of a &light pipe' made of a glass fibre of refractive inde($ )he outer covering of the pipe is made of a material of refractive inde( What is the range of the angles of the incident rays with the a(is of the pipe for which total reflections inside the pipe ta*e place, as shown in the figure$ (b)  What is the answer if there is no outer covering of the pipe+-. (a) /efractiveinde( of theglass fibre$ /efractiveinde( of the outer covering of the pipe0ngle of incidence 0ngle of refraction 0ngle of incidence at the interface )he refractive inde( of the inner core 1outer core interface is given as!  λ  =  π φ   = I1111 cos R I I I I I  π  = + + 111 1 I I I   = + − =    ÷   ( ) 1 1 < R K I I = =  λ  < K  1&EJ1&<<& 1 ,1&EJ  µ   =  ,1&<<  µ   = i = r  = : i = ( )  µ 
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