Option G 2: Lenses. The diagram below shows the image of a square grid as produced by a lens that does not cause spherical aberration.

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1 Name: Date: Option G 2: Lenses 1. This question is about spherical aberration. The diagram below shows the image of a square grid as produced by a lens that does not cause spherical aberration. In the space below, draw a possible shape of this image, as produced by a lens that causes spherical aberration. Describe one way in which spherical aberration can be reduced (Total 4 marks) 2. This question is about image formation by a converging lens. Define the principal focus (focal point) of a converging lens

2 An object is placed 30 cm in front of a converging lens of focal length 15 cm. The object is moved 5.0 cm closer to the lens. Determine the displacement of the image (Total 6 marks) 3. This question is about image formation by a converging lens. An object P is placed close to a converging lens as shown in the diagram below. The principal foci of the lens are marked. P lens On the diagram above, draw rays to locate the position of the image formed by the lens. Label this image with the letter I. The near point of an observer s eye is 25.0 cm from the eye. The lens in the diagram is positioned 4.0 cm from the lens in the observer s eye so as to form an image of the object P at the near point. The focal length of the lens is 8.0 cm. (i) Define the term near point. 2

3 Determine the distance from the object to the lens. (c) (i) Lenses are subject to chromatic aberration and spherical aberration. Describe and explain chromatic aberration and spherical aberration. Chromatic aberration: Spherical aberration Suggest how the effects of spherical aberration can be reduced. (Total 12 marks) 3

4 4. This question is about converging lenses. The diagram shows a small object O represented by an arrow placed in front of a converging lens L. The focal points of the lens are labelled. O L (i) Define the focal point of a converging lens. On the diagram above, draw rays to locate the position of the image of the object formed by the lens. (iii) Explain whether the image is real or virtual. A convex lens of focal length 6.25 cm is used to view an ant of length 0.80 cm that is crawling on a table. The lens is held 5.0 cm above the table. (i) Calculate the distance of the image from the lens. 4

5 Calculate the length of the image of the ant. 5. This question is about lenses. (Total 10 marks) The diagram below shows a thin converging lens and an object, O. O The principal foci of the lens are at. Construct rays to locate the position of the image of the object. Describe fully the nature of the image formed

6 (c) The diagram below shows the relative positions of the objective lens and eyepiece lens used in a compound microscope in normal adjustment. objective lens eyepiece lens O An object O is placed in front of the objective lens. On the diagram above, draw the approximate positions of (i) (iii) (iv) the principal foci of the objective lens (label these with the letter A); the image formed by the objective lens (label this with the letter B); the principal foci of the eyepiece lens (label these with the letter C); the position of the final image (label this with the letter D). (d) Suggest why, for large magnifications, a compound microscope is used, rather than a single lens (Total 11 marks) 6

7 6. This question is about a telescope. The diagram below shows two lenses arranged so as to form an astronomical telescope. The two lenses are represented as straight lines. objective lens eye lens focal length f O focal length f E The focal lengths of the objective lens and of the eye lens are f O and f E respectively. Light from a distant object is shown focused in the focal plane of the objective lens. The final image is to be formed at infinity. Complete the ray diagram to show the formation of the final image. (i) State what is meant by angular magnification. Using the completed ray diagram above, derive an expression in terms of f O and f E for the angular magnification of an astronomical telescope. Assume that the final image is at infinity. (c) When specifying an astronomical telescope, the diameter of the objective lens is 7

8 frequently quoted. Suggest a reason for quoting the diameter (Total 8 marks) 7. This question is about magnification. An object is placed 3.0 cm from a converging (convex) lens of focal length 5.0 cm. On the diagram below, draw rays to locate the position of the image produced by the lens. 1.0 cm lens object ' On the diagram above, mark with the letter E, the position from which the image should be viewed. (c) Use your ray diagram above to calculate the magnification of the image (d) or high magnification, a compound microscope may be used. This microscope consists of an objective lens and an eyepiece lens. 8

9 (i) State the type of lens used as both the objective lens and the eyepiece lens. The magnification produced by the objective lens is 24. The image of the object produced by this lens is formed 3.4 cm from the eyepiece lens of focal length 4.0 cm. Determine the magnification of the final image produced by the microscope. (Total 11 marks) 9