Thursday 14 June 2012

PREVIOUS YEAR QUESTIONS (RAY OPTICS)

Q1) Derive the expression for the refractive index of the material of the prism in terms of the angle of the prism and angle of minimum deviation. Use this formula to calculate the angle of  minimum deviation for an equilateral triangular prism of refractive index 3^(1/2).[DELHI 2006C].

Q2) Draw a labeled ray diagram of an astronomical telescope for the near point adjustment.You are given three lenses of powers 0.5D,4D,10D.stare with reason which two lenses wll you select for constructing a good astronomical telescope.caculate the resolving power  assuming the diameter of this objective lens to be 6cm and the wavelength of light used to be 540nm.[DELHI 2006C]

Q3) (i) Draw a labelled ray diagram of a compound microscope,showing the formation of image at  the near point of the eye.
      (ii)A compound microscope uses an objective lens of focal length 4cm and eye lens of focal length 10cm.An object is placed at 6cm from the objective les.
        a)Calculate magnifying power of the compound microscope,if the final image is formed at the near point.
      b)Calculate the length of the compound microscope also. [AI 2006C]

Q4) Draw a labelled ray diagram of an astronomical telescope,forming the image at infinity.An astronomical telescope uses two lenses of powers 10D,1D.
      i)State with reasons,which lens is preferred as objective and eye-piece.
     ii)Caculate the magnifying power of the telescope,if the final image is formed at the near point.
    iii)How do the light gathering power of a telescope change if the aperture of the objective lens is doubled? [AI 2006C]

Q5) Draw a labelled ray diagram of an astronomical telescope used in the normal adjustment position.write the exression fo its magnifying power.
Two astronomical telescope T1 and T2 have the same magnifying power.The ratio of aperture of their objective is 3:2.
  i)Which one of the two produces image of greater intesity?
ii)Which one of the two has larger resolving power?
Explain your answer in each case.[FOREIGN 2006]

Q6) Draw labelled ray diagram showing the image formation by a compound microscope.Write the expression for its magnifying power.
Define the term resolving power of a compound microscope.How does the resolving power of a compound microscope change on.
   i)decreasing the diameter of its objective lens?
  ii)increasing the focal length of its objective lens?
justify your answer in each case. [FOREIGN  2006]


Q7) Show by a diagram the image formation of a point by a thin double convex lens having radii of curvature R1 and R2.Hence derive the formula 1/f=(n-1)(1/R1-1/R2),where f is the focal length and n is the refractive index of the material of the lens.[DELHI 2005C]

Q8)Draw a labelled diagram of a compound microscope when the image is formed at infinity.Deduce the expression for its magnifying power.How can the magnifying power be increased?[AI 2005C]

Q9)Draw a labelled diagram to show the image formation in an astronomical telescope.Write an expression for its magnifying power.Why should the objective lens of such a telescope have large diameter?[AI 2005C]

Q10)Draw a labelled ray diagram to show image formation by a terrestrial telescope.write expression for its magnifying power.
In a compound microscope,the focal length of the objective and the eye-piece are 1.0cm and 2.0cm,respectively.The tube length of the microscope is 20cm.Calculate its magnification.Why must both the objective and the eye-peice of a compund microscope have short focal lengths?
[FOREIGN 2005]

Q11) a) Derive the relation 1/f=1/v-1/u for a biconvex lens.How is the approximate value of the focal length of such a lens estimated in the laboratory?
        b)A beam of light converges to a point 'P'.A lens is placed in the path of the convergent beam 12cm from p.At what point does the beam converge if the lens is 
 i)a convex les of 20cm focal length 
ii)a concave lens of 16cm focal length?[FOREIGN 2005]

Q12) With the help of a ray diagram,show the formation of image of a point object by refraction of light at a spherical surface separating two media of refractive indices n1 and n2(n2 > n1)respectively.Using this diagram derive the relation

n2/v-n1/u=n2-n1/R
Write the sign convention used.What happens to the focal length of convex lens when it is immersed in water?[DELHI 2004]

Q13) A spherical surface of radius of curvature R separates rare and a denser medium as shown in the figure. Complete the path of the incident ray of light showing the formation of a real image.Hence derive the relation connecting object distance 'u',image distance 'v',radius of curvature R and the refractive indices n1 and n2 of the media.
Breiefly explain,how the focal length of a convex lens chanes with increase in wavelength of incident light. [AI 2004]

Q14)Draw a ray diagram to show the formtion of the image of a point object placed in a medium of refreactive index n1 on the principal axis of a convex spherical surface of radius of curvature R and refractive index n2.Using the diagram derive the relation n2/v-n1/u=n2-n1/R.

A converging lens of focal length 50cm is placed coaxially in contact with another lens of unknown focal length.If the combination behave like a diverging lens of focal length 50cm,find the power and nature of he second lens. [AI 2004C]

Q15) Draw a ray diagram to show the formation of the image of a distant object by an astronomical telescope in the normal adjustment position.Obtain an expression for the magnifying power of the telescope in this adjustment.Define resolving power of a telescope.How would it change with the increase of
i)aperture of the ojective 
ii)Wavelength of light? [AI 2004C]

Q16)How would you estimate rough focal length of a converging lens?
Draw a ray diagram to show the image formation by a diverging lens.Using this diagram derive the relation between object distance 'u',image distance 'v' and the focal length 'f' of the lens.Sketch the graph between 1/u and 1/v for this lens.[Foreign 2004]

Q17)Define magnifying power of an optical telescope.
        Draw a ray diagram for an astronomical refracting telescope in normal adjustment showing the paths through the instrument of three rays from a distant object.Derive an expression for its magnifying power.
Write the significance of diameter of the objective lens on the optical performance of a telescope.[FOREIGN 2004]

Q18)A lens forms a real image of an object.The distance from the object to the lens is u cm and the distance of the image from the lens is v cm.The given graph shows variation of u with v.
 i) What is the nature of the lens?
ii)Using the graph,find the focal length of this lens.
Draw a ray diagram to show the formation of real imageof the same size as that of the object placed in front of a converging lens.Usig this ray diagram establish the relation between u,v and f for this lens.[Foreign 2004]
Q19)Derive the relation between distance of the object,distance of the image and the radius of curvature of a convex spherical surface,when refraction takes place from a rarer medium of refractive index u1 to a denser medium of refractive index u2 and the image produced is real.State assumptions and conventions of signs used. [DELHI 2003]

Q20)Draw a ray diagram to show the formation of the image of an object placed between the optical centre and focus of the convex lens.Write the characteristics of the image formed.Using this diagram,derive the relation between object distance,image distance and focal length of the convex lens.Write the assumptions and convention of signs used.[DELHI  2003]

Q21)Draw a ray diagram to show the formation of the real image of a point object due to a convex spherical refracting surface,when the ray of light is travelling from a rarer medium of refractive index u1 to a denser medium of refractive index u2.
Using this diagram,derive the relation between object distance(u),image distance(v),radius of curvature(R) of a convex spherical surface.State the sign convention and the assumptions made.[Delhi 2003C].

Q22) Draw a ray diagram for the formation of image of a distant object by an astronomical telescope in normal adjustment position.
Deduce the expresssion for its magnifying power.How does the resolving power of a telescope change if
i)the size of the aperture of the objective lens is decreased and increased.[Delhi 2003C]

Q23)Using the data given below,state which of the given lenses will you use an eyepiece and as an objective to construct an astronomical telescope.

LENSES                          POWER                     APERTURE
L1                                     3D                              8cm
L2                                     6D                              1cm
L3                                     10D                            1cm

Draw a ray diagram to show the formation of the image of a distant object in the normal adjustment position for the astronomical telescope so formed.Write the expression for its
i)magnifying power
ii)length of the telescope. [FOREIGN 2003]

Q24)Using th data given above for lenses L1,L2,L3,state which of the given lenses will you use as an objective and eyepiece to construct a compound microscope.
Draw ray diagram to show the formation of the image of a tiny object by this compound microscope.Write the expression for its magnifying power.how can magnifying power of a compound microscope be increased? [FOREIGN 2003]

Q25) Two lenses of power +15D and -5D are in contact with each other forming a combination lens.
a)What is the focal length of this combination?
b)An object of size 3cm is places at 30cm from this combination of lenses.Caculate the position and size of the image formed.[DELHI 2002]

Q26)Two lenses of power -15D abd +5D are in contact with each other forming a combination lens.
 a)What is the focal length of this combination?
b)An object of size 4cm is placed at 20cm from this combination of lenses.Calculate the position and size of the image formed.[DELHI 2002]

Q27)Derive the relation between distance of object,distance of image,and radius of curvature of a convex spherical surface,When refraction takes place from a rarer to denser medium and image produced is virtual.State the assumptions and conventions of sign used.[AI 2002C]

Q28)Explain with reason,how the resolving power of a compound microscope will change when i)frequency of the incident light on the objective lens is increased
ii)focal length of the objective lens is increased
iii)aperture of the objective lens is increased.[AI 2002]

Q29)A ray of light is incident at an angle of incidence i on the surface separating air and a denser medium of refractive index 'n',such that the reflected and refracted rays of light are at right angles to each other.Derive The relation connecting n and i.[FOREIGN 2002]

Q30)Give reasons for the following :
a)Sky appears blue during day time as seen from earth.
b)A rainbow is never observed from surface of moon.
c)Sunset and sunrise are abrupt as seen from moon. [FOREIGN 2002]

Q31)For a converging lens r1=r2=24cm and refractive index 1.6
i)calculate its focal length in air
ii)if the lens is split vertically into two identical parts,what is the focal length of each part? [FOREIGN 2002]

Q32)You are given two convex lenses of short aperture having focal length 4cm and 8cm respectively.Which one of these will you use as an objective and which one as an eyepiece
Draw a ray diagram to show the formation of the image of a small object due to a compound microscope.Derive an expression for its magnifying power.[DELHI 2001C]

Q33)With the help of a ray diageam explain the phenomenon of total internal reflection.Obtain the relation between critical angle and the refractive index of the medium.Draw ray diagram to show how a right angled isosceles prism can be used to
i)deviate the ray through 180 degrees
ii)deviate the ray through 90 deg
iii)invert the ray [DELHI 2001C]

Q34)With the help of a ray diagram,explain the formation of image in an astronomical telescope for a distant object.Define the term Magnifying power of a telescope.Derive an expression for ts magnifying power when the final image is formed at least distance of distinct vision.[AI 2000C]

Q35)Explain the phenomenon of total internal reflection.State two condition that must be statisfied for the total internal reflecion to take place.Derive the relation between the critical angle and the refractive indiex 0f the medium.Draw a ray diagram to show how a right angled isosceles prism can be used to
i)deviate ray through 180 deg
ii)to invert it.[AI 2000C]

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