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प्रश्न
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.
उत्तर
A person must hold his face at a distance of 20 cm , away from the concave mirror. A concave mirror forms an erect, virtual and magnified image when an object is placed between the focus and the pole. Therefore, it acts as a shaving mirror.
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संबंधित प्रश्न
Consider the following diagram in which M is a mirror and P is an object and Q is its magnified image formed by the mirror.
State the type of the mirror M and one characteristic property of the image Q.
Name the mirror that can give an erect and enlarged image of an object.
A concave mirror produces three times magnified image on a screen. If the object is placed 20 cm in front of the mirror, how far is the screen from the object.
Make labelled ray diagrams to illustrate the formation of:
a virtual image by a converging mirror.
Mark clearly the pole, focus, centre of curvature and position of object in each case.
Briefly describe how you would find the focal length of a concave mirror quickly but approximately
In the concave reflector of a torch, the bulb is placed:
(a) between the pole and focus of reflector
(b) at the focus of reflector
(c) between focus and centre of curvature of reflector
(d) at the centre of curvature of reflector
Draw and complete the following diagrams to show what happens to the beams of light as they enter the glass block and then leave it:
Answer the following question:
An object is placed at a distance of 30 cm from a concave lens of focal length 30 cm.
(i) Use the lens formula to determine the distance of the image from the lens.
(ii) List four characteristics of the image (nature, position, size, erect/inverted) in this case.
(iii) Draw a labelled diagram to justify your answer of the part (ii)
According to cartesion sign convention, which mirror and which lens has negative focal length?
In the headlights of motor vehicles, ______ mirrors are used as reflectors.
