Ask a Doubt
Request a call back

Join NOW to get access to exclusive study material for best results

CBSE Class 10 Answered

A screen bearing a real image of magnification m1,formed by a convex lens,is moved by a distance x.The object is then moved until a new image of magnification m2 is formed on screen.The focal lenght of lens is: (1) . x/m2-m1 (2) . m2-m1/x (3) . x/m1-m2 (4) . m1-m2/x
Asked by dfojajjar | 16 Feb, 2020, 01:35: PM
answered-by-expert Expert Answer
We have lens formula :-  (1/v) - (1/u) = 1/f  ..............(1)
 
where v is lens-to-image distance, u is lens-to-object distance and f is focal length
 
By multiplying eqn.(1) with v, we get ,  1 - (v/u) = (v/f)
 
since magnification m of the image is given by, m1 = (v/u),
 
then we get from above equation, 1 - m1 = (v/f)  ...................(2)
 
if image-to-lens distance is changed to v+x, then magnification becomes m2
 
Equation (2) with new magnification m2 is written as ,  1 - m2 = (v+x)/f  = (v/f) + (x/f)  ...........(3)
 
Substituting for (v/f) from eqn.(2) in eqn.(3), we get,  1- m2 = 1 - m1 + (x/f)
 
Hence we get ,  (x/f) = [ m1 - m2 ]  ,   hence  focal length f = x / [ m1 - m2 ]
 
 
 
Answered by Thiyagarajan K | 16 Feb, 2020, 05:06: PM

Application Videos

Concept Videos

Multiple Choice Questions Practice Test Subjective Questions Webinar Subjective Questions Pre Board Assessment
Answered Unanswered My Questions My Answers
CBSE 10 - Physics
the angle between an incident ray and the reflecting surface is 55°. what will be the total angle between the incident and reflected ray?
Asked by ruchipandey20071978 | 11 May, 2023, 06:53: AM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Physics
a concave mirror has a radius of curvature of 0.4m. find the position and size of the image of an object placed 0.2m high and is placed 0.8m in front of a concave mirror.
Asked by priyanshdhiman2008 | 17 Mar, 2023, 09:17: AM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Physics
An object at distance of 24cm is placed in front of Concave. mirror having focal length 10cm. find image distance. Nature of image and magnification
Asked by piustoppo9thb | 24 Jun, 2022, 09:58: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Physics
if a plane mirror is rotated by an angle of theta by how much will the angle between the incident and the reflected ray change?
Asked by priyankakiran2017 | 22 Jun, 2022, 07:07: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Physics
Mirror formula
Asked by topperlearningforcontent | 02 Feb, 2022, 03:32: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Physics
The distance between the real object and its image in a convex mirror of focal length 12 cm is 32 cm. the size of the object is 1cm. the object distance will be
Asked by bibektripathy17 | 15 Jun, 2021, 09:13: AM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Physics
when we reverse the image then image will formed or not
Asked by vkpriya1228 | 24 Apr, 2021, 08:04: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Physics
A REAL OBJECT IS LOCATED IS LOCATED AT ZERO END OF A METER STICK. A CONCAVE MIRROR LOCATED AT 100 cm END OF THE METER STICK FORMS AN IMAGE OF THE OBJECT AT THE 70cm POSITION. A CONVEX MIRROR PLACED AT THE 60cm POSITION FORMS A FINAL IMAGE AT THE 10 cm POINT WHAT IS THE RADIUS OF CURVATURE OF THE CONVEX MIRROR?
question image
Asked by iraza2663 | 21 Apr, 2021, 09:18: AM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Physics
A concave mirror produces three times magnified (enlarged) real image of an object placed at 10cm in front of it . Where is the image located?
Asked by grexiemalinnie | 17 Jan, 2021, 09:15: AM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Physics
why presently sign convention is known as new sign convention
Asked by alimohd1487 | 03 Jan, 2021, 06:40: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
My Class Videos Tests ₹ Plans Ask a Doubt