47. Read the text carefully and answer the questions: Hold a concave mirror in your hand and direct its reflecting surface towards the sun. Direct the light reflected by the mirror on to a white card-board held close to the mirror. Move the card-board back and forth gradually until you find a bright, sharp spot of light on the board. This spot of light is the image of the sun on the sheet of paper; which is also termed as Principal Focus of the concave mirror. (a) (b) (c) (d) Concave mirror SO Principal Focus Principal axis List two applications of concave mirror. If the distance between the mirror and the principal focus is 15 cm, find the radius of curvature of the mirror. Draw a ray diagram to show the type of image formed when an object is placed between pole and focus of a concave mirror. An object 10 cm in size is placed at 100 cm in front of a concave mirror. If its image is formed at the same point where the object is located, find: i. focal length of the mirror, and ii. magnification of the image formed with sign as per Cartesian sign convention. 48. Read the text carefully and answer the questions: A student took three concave mirrors of different focal lengths and performed the experiment to see the image formation by placing an object at different distances with these mirrors as shown in the following table. Case No. Object-distance Focal length 45 cm 20 cm I II 30 cm 15 cm 30 cm III 20 cm (a) List two properties of the image formed in Case I. (b) (c) Name the type of mirror used by dentists. Give reason why do they use such type of mirrors. (d) In which one of the cases given in the table, the mirror will form real image of same and why? Look at the table and identify the situation (object distance and focal length) which resembles the situation in which concave mirrors are used as shaving mirrors? Draw a ray diagram to show the image formation in this case.