Advertisements
Advertisements
प्रश्न
A converging mirror forms a real image of height 4 cm of an object of height 1 cm placed 20 cm away from the mirror:
- Calculate the image distance.
- What is the focal length of the mirror?
उत्तर
A concave mirror is a converging mirror.
Distance of the object from the mirror μ = −20 cm
Height of the object ho = 1 cm
Height of the image hi = v4 cm
We have to find the distance of the image v and the focal length of the mirror f.
Using the magnification formula, we get
`m = h_i/h_o = (-v)/u`
⇒ `(-4)/1 = (-v)/-20`
`v = 20 xx (-4)/1 = -80` cm
Thus, the distance of the image v is 80 cm.
Now, using the mirror formula, we get
`1/f = 1/v + 1/u`
`1/f = 1/-80 + 1/-20`
= `-1/80 -4/80`
= `-5/80`
`1/f = -1/16`
f = −16 cm
Thus, the focal length of the concave mirror is −16 cm.
APPEARS IN
संबंधित प्रश्न
A student has obtained the image of a distant object with a concave mirror to determine its focal length. If he has selected a well-illuminated red building as object, which of the following correctly describes the features of the image formed?
(A) Virtual, inverted and diminished image in red shade
(B) Real, erect and diminished image in pink shade
(C) Real, inverted and diminished image in red shade
(D) Virtual, erect and enlarged image in red shade
We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case.
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.
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.
Giving reasons, state the 'signs' (positive or negative) which can be given to the following:
(a) object distance (u) for a concave mirror or convex mirror
(b) image distance (v) for a concave mirror
(c) image distance (v) for a convex mirror
Radius of curvature of a spherical mirror is ............. its focal length.
For a real object, which of the following can produce a real image?
Rays from Sun converge at a point 15 cm in front of a concave mirror. Where should an object be placed so that size of its image is equal to the size of the object?
The ENT doctor uses a ______.
