When an object is placed at a distance of 25 cm from a mirror, the magnification is m 1 . The object is moved 15 cm away with respect to the earlier position along principal axis, magnification becomes m 2 . If m 1 × m 2 = 4, the focal length of the mirror in cm is…. × 10 cm.
Text Solution
Verified by ExpertsThe correct answer is:
CHECK THE SOLUTION.
Ans. 5
Sol. 
= 
– 
v = 
m = 
= 
m 1 × m 2 = 4
= 4
f 2 = 4 [f 2 – 65 + 1000] = 0
3f 2 – 260f + 4000 = 0 ⇒ f = 20
Prepare Smarter with CGP Edu
Get practice questions, solutions, and test series in one place.
Write a Review
Share your experience with this question and solution.
Commentary
Send your comment, doubt, correction, or feedback to admin.
Similar Questions
Explore conceptually related problems
A student can distinctly see the object upto a distance 15 cm . He wants to see the black board at …
Two plane mirrors. A and B are aligned parallel to each other, as shown in the figure. A light ray …
A concave mirror of focal length is used to obtain the image of the sun which subtends an angle of…
A square of side is placed at a distance of from a concave mirror of focal length The centre of …
A thin rod of length lies along the axis of a concave mirror of focal length One end of its magni…
A ray of light falls on the surface of a spherical glass paper weight making an angle with the nor…