Case Based Questions Test: Light- Reflection & Refraction - 2 - Class 10 MCQ

Since we know that virtual image is formed only in case when the object is placed in between focus and pole of concave mirror. The image formed is erect and magnified (or) enlarged.

It can be expressed as : Linear Magnification, ⇒ Linear magnification, This shows that the linear magnification produced by a mirror is also equal to the ratio of the image distance (v) to the object distance (u) with a minus sign.

you can see, case (iii); here both the object and the image distances are 30cm .but we know this is possible only case when object kept at 2f, so, 2f = 30cm => f = 15cm
(b) use lens formula for finding incorrect observations.
1/v - 1/u = 1/f
see last observation (v)
u = -15
f = +15
then, 1/v = 1/15 - 1/15 = 0 = 1/∞ => v = ∞
but v = 70cm is given hence, observation (v) is wrong.
(c) obviously case 3 , in this case size of image is equal to size of object due to image distance distance is equal to object distance from pole.

you can see, case (iii); here both the object and the image distances are 30cm .but we know this is possible only case when object kept at 2f, so, 2f = 30cm => f = 15cm
(b) use lens formula for finding incorrect observations.
1/v - 1/u = 1/f
see last observation (v)
u = -15
f = +15
then, 1/v = 1/15 - 1/15 = 0 = 1/∞ => v = ∞
but v = 70cm is given hence, observation (v) is wrong.
(c) obviously case 3, in this case size of image is equal to size of object due to image distance distance is equal to object distance from pole.

you can see, case (iii); here both the object and the image distances are 30cm .but we know this is possible only case when object kept at 2f, so, 2f = 30cm => f = 15cm
(b) use lens formula for finding incorrect observations.
1/v - 1/u = 1/f
see last observation (v)
u = -15
f = +15
then, 1/v = 1/15 - 1/15 = 0 = 1/∞ => v = ∞
but v = 70cm is given hence, observation (v) is wrong.
(c) obviously case 3, in this case size of image is equal to size of object due to image distance distance is equal to object distance from pole.