| Previous Year Questions of March Examinations from 2010 to 2020 |
| Chapter Name: RAY OPTICS AND OPTICAL INSTRUMENTS |
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Combination of lenses are used in optical instruments to obtain the required power. a) What do you mean by power of a lenses? Express its unit. b) Draw a neat schematic ray diagram for the formation of image due to a point object placed in front of two thin convex lenses placed in contact. c) Obtain an expression for the effective focal length of the combination of two thin convex lenses in contact |
| Figure shows a graph between angle of incidence and the respective deviation of light when it is passed through an optical element. (b) Using a schematic diagram derive an expression for the fringe width in Young’s double slit experiment. a) Name this optical element. b) What will happen to the angle of minimum deviation D if it is completely immersed in water? Justify your answer. c) Obtain an expression for the refractive index of the material of this optical element. |
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A lens of a particular focal length is mode from a given glass slab by adjusting radii of curvature. The formula used in this case is lens maker’s formula. a) Write lens maker’s formula. b) Derive lens maker’s formula assuming formula for refraction at a spherical surface. c) Is it possible for a given lens to act as a converging lens in one medium and a diverging lens in another medium? Why? d) Compare the focal length of a given converging lens for the blue light with that using red light are they equal or different? Why? |
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A microscope is a device used to obtain magnified imaged of small objects. a) Draw a labelled ray diagram of a compound microscope forming an image at the near point of the eye b) Obtain an expression for the magnifications produced by a compound microscope. c) If the objective lens is immersed in a transparent oil, what will happen to the resolving power of the microscope? Explain. |
| Using the data given in figure, state as to which of the given lenses will you prefer to use as i) an eye-piece and ii) an objective to construct an astronomical telescope? Give reason for your answer. |
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a) A spherical surface of radius of curvature R separates a rarer and a denser medium . b) With the help of a ray diagram, derive the relation connecting object distance ‘u’, image distance ‘v’, radius of curvature R and the refractive indices n1 and n2 of the two media. c) A thin convex lens of focal length 5 cm is used as a simple microscope by a person with normal near point (25 cm). What is the magnifying power of the microscope? |
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Consider a ray incident on a prism ABC. a) Complete the ray diagram showing the passage of light. Mark angle of incidence i, angle of emergence e, angle of deviation δ and angle of refraction r1 and r2 . b) Using the diagram obtain the relation δ = i + e - A c) The critical angle for diamond is 300 . What is its refractive index? |
| A) An equilateral glass prism is placed on a horizontal surface. A ray PQ is incident on it. For minimum deviation: i) PQ is horizontal ii) QR is horizontal iii) RS is horizontal iv) None of these B) A thick lens gives coloured images due to .............. C) In a compound microscope the nature of the intermediate image is ...... D) Based on refraction and total internal reflection, explain the formation of rainbow |
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Light has several properties like reflection, refraction etc. When light travels from an optically denser medium to a rarer medium? a) What happens to the light at the interface? b) Give demonstration for total internal reflection c) What are the technological applications of total internal reflection in nature? Briefly explain it |
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(A) A convex lens (a) is thicker at the edges than at the middle (b) is thicker at the middle than at the edges (c) diverges rays of light (d) is of uniform thickness everywhere (B) With the help of a ray diagram sketch the image formation by a convex lens, when the object is between C and F (C) Derive the Lens Maker’s formula |
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(A) a ray of light travels from a denser medium to a rarer medium, then the ray (a) doesn’t bend at all (b) bends towards the normal (c) bends away from the normal (d) goes along the normal (B) Draw a diagram showing the path of a monochromatic beam of light through a triangular prism (C) Using this diagram obtain the relation for Refractive Index |
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(a) If the focal length of a double convex lens is 12 cm and radii of curvatures of faces are 10 cm and 15 cm respectively, what is the refractive index of the lens? (b) (i) Draw the ray diagram showing the formation of image by a compound microscope (ii) Show that in order to achieve large magnification in a compound microscope the magnitude of focal length of objective and eye piece should be small |
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(a) What is the structure of an optical fibre? (b) What is the principle used for transmitting audio and video signals using optical fibre? Explain the principle (c) With the help of a neat diagram arrive at an expression for finding the refractive index of a prism |
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A concave lens always produces…………... images (i) real (ii) virtual (iii) magnified (iv) none of these |
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(a) Speed of light in glass is 2x 108 m/s. Refractive index of glass is .......... (b) For an equilateral prism made of a material of refractive index 1.414, find the angle of minimum deviation for a ray of monochromatic light. (c) Draw the ray diagram of a simple microscope that uses a single convex lens. Derive an expression for its linear magnification |
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Two thin convex lenses of focal lengths f1 and f2 are placed in contact (a) If the object is at principal axis draw ray diagram of the image formation by this combination of lenses (b) Obtain a general expression for effective focal length of the combination in terms of f1 and f2 |
| A ray of light passing through a prism. If the refracted ray OR is parallel to the base BC, as shown in figure. (a) Derive an expression to find out deviation (d). (b) Draw a graph which shows the variation of d with i (c) Calculate the angle of minimum deviation if A = 60° and refractive index of the material of prism is 1.62. |
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A small telescope has an objective lens of focal length 140 cm and an eyepiece of focal length 5 cm. What is the magnifying power of the telescope for viewing distant objects when (a) the telescope is in normal adjustment. (b) the final image is formed at the least distance of distinct vision. |
| A ray of light parallel to the principal axis of a spherical mirror falls at a point M as shown in the figure (a) Identify the type of mirror used in the diagram (b) By drawing a suitable ray diagram, obtain the mirror equation. (c) If the mirror is immersed in water, its focal length ................ (increases / decreases / remain the same) |
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Total internal reflection may be observed if (a) light ray is travelling from denser medium to rarer medium (b) light ray is travelling from rarer medium to denser medium (c) light ray is travelling from any medium to another medium |
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Optical fibres make use of the phenomenon of (a) refraction (b) total internal reflection (c) interference (d) diffraction |
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A magician during a show makes a glass lens with n = 1.47 disappear in a trough of liquid. (a) What is the refractive index of the liquid ? (b) Could the liquid be water ? |
| Explain why the bluish colour predominates in a clear sky. |
| The figure shows the image formation of an object in simple microscope. (a) Find out the object distance and image distance from the figure. (b) Derive an equation for magnifying power of the simple microscope. |
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