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PHYSICS SCIENCE Paper 1 REFRACTION AND LENSES (2 hours) Answers to this Paper must be written on the paper provided separately. You will not be allowed to write during the first 5 minutes. This time is to be spent in reading the Question Paper. The time given at the head of this Paper is the time allowed for writing the answers. ____________________________________________________________________ Attempt all the questions from Section I and Section II The intended marks for questions or parts of questions are given in brackets [ ]. SECTION I (40 Marks) Attempt all questions from this Section Question 1 (a) What do you mean by lateral displacement? Explain with the help of a labeled diagram. [2] (b) Define critical angle. How does critical angle of a medium depend upon the wavelength of incident light? [2] (c) Mention two major differences between image formation in a total reflecting prism and a plane mirror. [2] (d) How does angle of incidence depend upon angle of deviation? Explain using i- curve. [2] (e) The power of a lens is -2.D. Find the focal length and state the kind of lens. [2] Question 2 (a) Draw a ray diagram to show the application of a diverging lens as a lens used to correct myopia. [2] (b) How does refractive index depend upon: (i) Critical angle (ii) Angle of incidence [2] (c) Define total internal reflection. Also state the conditions for TIR. [2] (d) What do you understand by magnification? What type of lens has its magnification always less than 1? [2] (e) When a ray of light passes from air to glass, for what angle of incidence, the ray will not be deviated? [2] Question 3 (a) Copy and complete the following diagrams to show the path of the ray of monochromatic light in each case as it enters and emerges out of the prism. Mark the angle wherever necessary (critical angle is 42 ) [2] (i) (ii) (b) Calculate the refractive index of a liquid with respect to air applying Snell's law (use geometric construction). [2] (c) Abhijeet claims to have obtained an image twice the size of object using a concave mirror. Is he correct? Give reasons for your answer. [2] (d) You are provided with a printed piece of paper. How will you distinguish between a convex and a concave lens using the paper? [2] (e) We can burn a piece of paper by focusing sun rays using a particular type of lens. Mention the type of lens used. Also draw a ray diagram to show the same. [2] Question 4 (a) Copy and complete the following table: [2] (b) Draw a diagram to illustrate the determintion of focal length of a convex lens using an auxiliary plane mirror. [2] (c) An object is placed in front of a converging lens at a distance greater than twice of the focal length of the lens. Draw a ray diagram to show the formation of the image. [2] (d) The diagram shows a point source of light s, a convex lens L and plane mirror M. These are placed such that rays of light from s, return to it after reflection from M. (i) What is the distance OS called? (ii) To which point (left of S or right of S) will the rays return if M is moved to the left and attached with the lens L. [2] (e) A postage stamp appears to be raised by 7.0 mm, when placed under a rectangular block of refractive index 1.5. Find the thickness of the glass block. [2] SECTION II (40 Marks) Attempt all questions from this Section Question 5 (a) (i) Define one diopter. (ii) An object of height 7cm is placed at a distance of 12cm from a convex lens of focal length 8cm. Find the position and nature of the image using lens formula. [4] (b) Draw a diagram to show how a total refracting prism can be used to deviate the light rays by 180o. Also mention the application of such arrangement. [4] (c) State Snell s law of refraction. Question 6 [2] (a) Show with the help of a diagram that a stick kept obliquely in water appears to bend. [3] (b) Draw a ray diagram to show how a convex lens can be used as a magnifying glass. [3] (c) (i) Give one condition for minimum deviation of light in a prism. Also draw the well labeled diagram of the path of monochromatic light when kept at its angle of minimum deviation. [4] Question 7 (a) (i) Copy and complete the diagram to show the formation of the image of an object AB. (ii) Name the lens LL (iii) What is the special name given to point X? (iv) Mention one application of such arrangement. [4] (b) (i) Complete the diagram and answer the questions that follows. (ii) What is the angle of incidence on face AB and AC? (iii) Which surface of the prism acts as a plane mirror? [4] (c) PQ and QR are two light rays emerging from the object P as shown in the figure. (i) What is the special name given to the angle of incidence PQN of the ray PQ. (ii) Copy the ray diagram and complete it to show the position of image of the object P, when seen obliquely from above. (iii) Name the phenomenon that occurs if the angle of incidence PQN is increased further. [4] Question 8 a) (i)The type of glass which produce greater deviation of glass prism is (flint/crown) ? (ii) How does refractive index depends upon the critical angle and the wavelength of light? [3] (b) Using two isoceles right angled prism, deviate the light in the following way [3] (c) (i) A 4cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 20cm. If the distance of the object is 30cm from the lens, find the position, nature and size of the image. Also find its magnification. [3] (ii) One-half of a convex lens is covered with a black paper. What will happen to the image formed? [1]
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