A concave mirror has a focal length of 25 cm. At which of the following distance should a person hold his face from this concave mirror so that it may act as a shaving mirror ? (a) 45 cm (b) 20 cm (c) 25 cm (d) 30 cm Give reason for your choice.

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Solution

20 cm, because if the object is placed between the pole and focus of the concave mirror only then the image formed is erect and magnified.ie, for shaving we need irrect and magnified image.

Diagram(Object between Principal Focus (F) and Pole (P)):

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A concave mirror has a focal length of 25 cm. At which of the following distance should a person hold his face from this concave mirror so that it may act as a shaving mirror ? (a) 45 cm (b) 20 cm (c) 25 cm (d) 30 cm Give reason for your choice.

20 cm, because if the object is placed between the pole and focus of the concave mirror only then the image formed is erect and magnified.ie, for shaving we need irrect and magnified image. Diagram(Object between Principal Focus (F) and Pole (P)):

20 cm, because if the object is placed between the pole and focus of the concave mirror only then the image formed is erect and magnified.ie, for shaving we need irrect and magnified image.

Diagram(Object between Principal Focus (F) and Pole (P)):