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प्रश्न
When an object is placed at a distance of 15 cm from a concave mirror, its image is formed at 10 cm in front of the mirror. Calculate the focal length of the mirror.
उत्तर
Distance of the object from the mirror 'u' = −15 cm
Distance of the image 'v' = −10 cm
We have to find the focal length of the mirror 'f'.
Using the mirror formula, we get
`1/f=1/v+1/u`
`1/f=1/(-10)+1/(-15)=-1/10-1/15`
`1/f=-3/30-2/30`
`1/f=-5/30`
f=-6 cm
Thus, the focal length of the concave mirror 'f' is 6 cm.
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संबंधित प्रश्न
Draw ray diagrams to show the principal focus of a convex mirror.
A spherical mirror and a thin spherical lens have each a focal length of -15 cm. The mirror and the lens are likely to be ______.
Draw a ray diagram showing how a concave mirror can be used to produce a real, inverted and diminished image of an object.
Briefly describe how you would find the focal length of a concave mirror quickly but approximately
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.
An object is placed at a distance of 10 cm from a concave mirror of focal length 20 cm.
Calculate the image distance.
An object is placed at a large distance in front of a concave mirror of radius of curvature 40 cm. The image will be formed in front of the mirror at a distance:
(a) 20 cm
(b) 30 cm
(c) 40 cm
(d) 50 cm
Radius of curvature of a spherical mirror is ............. its focal length.
State two uses of a concave mirror.
Write the uses of the concave mirror.
