Ray Optics-Important Questions & Preparation Tips

In this article you will get the clue that from where and how the questions are being framed from chapter Ray Optics

CBSE Class 12th Chapter, Ray Optics comes under the topic Optics which carries 14 Marks in board exam. Experts of Jagranjosh.com offer the best practice material that covers all important questions so that students will not miss any portion while preparing for board exams or competitive exams. Consider the mentioned terms/questions at the time of studying.

  • A convex lens is held in water. What change, if any, do you expect in its focal length?
  • What happens to light wave falling normally to glass slab?
  • State the laws of reflection and refraction?
  • Which of the following remains unchanged during refraction:

      a) Wavelength
      b) Speed
      c) Intensity of light
      d) Frequency

  • Why does refraction occur when light passes from one medium to another?
  • Can absolute refractive index of a medium be less than 1? Can refractive index of a medium relative to another medium be less than 1?
  • Define critical angle for an interface of two media?
  • Can total internal reflection occur when light travels from rarer to denser medium?
  • A rod immersed partially or obliquely in water appears to be bent. Explain.
  • To a fish underwater, a man standing on the bank appears taller or shorter than his actual height? Why.
  • Differentiate between optical density and mass density?
  • Consider a glass sphere silvered from outside having a radius R. Bisect a small piece from the  sphere such that the inner surface act as a mirror:

     a) What would be the focal length of the bisected piece?
     b) Give the radius of curvature of the bisected piece?
     c) What would be the image distance if the object distance is R/3.
     d) What will happen if the upper half of the mirror is covered with an opaque material?

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  • Why are rays falling over a mirror or a lens considered to be paraxial?
  • Derive the mirror equation?
  • The refractive index of diamond is much greater than glass? Does diamond cutter use this fact.
  • Sun when near the horizon, appears elliptical and not circular. Why?
  • Why does star appear twinkling at night?
  • Explain the illusion, mirage seen on a hot summer day in desert?
  • On what principle does the optical fiber work? How are they useful in transmitting signals?
  • Explain the term photometry?
  • Derive the Len’s maker’s formula?
  • What could be done to disappear a glass in a liquid?
  • How can the sharpness of an image be enhanced?
  • How do thin prisms deviate light?
  • Give a brief account on refraction through prism?
  • Show that the deviation produced by a thin glass prism placed in air is reduced to one-fourth when the prism is immersed in water. Given: ang = 3/2 and anw = 4/3.
  • A ray of light incident on an equilateral glass prism shows minimum deviation of 300. Calculate the speed of light through the glass prism.
  • Prove that there is no emergent ray when the angle of prism is greater than twice the critical angle.
  • A Plano-convex lens has radius of curvature 10 cm. Its focal length is 80 cm under water. Calculate the refractive index of the material of the lens; given refractive index of water 4/3.
  • The distance between two point sources of light is 24 cm. Find out where you would place a converging lens of focal length 9 cm, so that the images of both the sources are formed at the same point.
  • The power of a thin convex lens of glass is 5D. When it is immersed in a liquid, then it behaves like a divergent lens of focal length 100 cm. Calculate the refractive index of the liquid. The refractive index of glass is 1.5.
  • Smoky flame of Bunsen burner gives continuous spectrum, whereas its blue flame gives band spectrum. Explain?
  • Why there is no dispersion in white light refracted through a rectangular glass slab?
  • White light passing through a hollow prism does not produce spectrum?
  • Rays of red and blue light are incident on a given prism. Explain which will have the larger angle of minimum deviation?
  • A person cannot see distinctly any object placed beyond 40 cm from his eye. Calculate the power of the lens which will help him to see distant object clearly?
  • On what factors does the resolving limit of the telescope depend?
  • Very distant objects which are not visible to eye are visible through telescope. Why?
  • In a compound microscope, both the objective and the eyepiece should be of small focal lengths. Why?
  • Write a short note on:

      a) Compound Microscope
      b) Telescope
      c) Human Eye
      d) Formation of rainbow

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  • Which glass the crown glass or the flint glass is more suitable for spectacle lens and why?
  • Visualize the diagram and answer the following questions:

   a) Which phenomenon is observed in at here?        
   b) Refractive index of glass and water are 4/3 and 3/2.The incident angle is 450. What would be the angle of refraction?
   c) Explain why a swimming  pool appears shallower than it actually is?
   d) Obtain an expression for the normal displacement of an object immersed in water?

  • Visualize the diagram and answer the following questions:

   a) Which lens is used in the given figure?
   b) Focal length of the lens (with refractive index = 1.5) is 20 cm. If the glass is immersed in a transparent liquid having refractive index 1.75. Find the new focal length?

  • You are given three lenses L1, L2 and L3 each of focal length 20 cm. An object is kept at 40. cm in front of L1, as shown. The final real image is formed at the focus ‘I’ of L3. Find the separations betweenL1, L2 and L3.

  • Trace the path of a ray of light passing through a glass prism (ABC) as shown. If the refractive index of glass is √3  find out the value of the angle of emergence from the prism.

  • Define power of a lens. Write its units. Deduce the relation

for two lenses kept in contact coaxially.

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