Q22.To find the focal length of a convex mirror, a student records the following data: Object pin Convex Lens Convex Mirror Image Pin 22.2 cm 32.2 cm 45.8 cm 71.2 cm The focal length of the convex lens is f1 and that of mirror is f2 . Then taking index correction to be negligibly small, f1 and f2 are close to: (1) f1 = 7.8 cm f2 = 12.7 cm (2) f1 = 12.7 cm f2 = 7.8 cm (3) f1 = 15.6 cm f2 = 25.4 cm (4) f1 = 7.8 cm f2 = 25.4 cm
What This Question Tests
This question requires applying both the lens formula and the mirror formula to experimental data to calculate the focal lengths of a convex lens and a convex mirror.
Concepts Tested
Formulas Used
1/f = 1/v - 1/u (lens)
1/f = 1/v + 1/u (mirror)
📚 NCERT Sections This Tests
9.19 — A Screen Is Placed 90Cm From An Object. The Image Of The Object On
Physics Class 12 · Chapter 9
9.19 A screen is placed 90cm from an object. The image of the object on the screen is formed by a convex lens at two different locations separated by 20cm. Determine the focal length of the lens.
9.2 — A 4.5 Cm Needle Is Placed 12 Cm Away From A Convex Mirror Of Focal
Physics Class 12 · Chapter 9
9.2 A 4.5 cm needle is placed 12 cm away from a convex mirror of focal length 15 cm. Give the location of the image and the magnification. Describe what happens as the needle is moved farther from the mirror.
9.8 — A Beam Of Light Converges At A Point P. Now A Lens Is Placed In The
Physics Class 12 · Chapter 9
9.8 A beam of light converges at a point P. Now a lens is placed in the path of the convergent beam 12cm from P. At what point does the beam converge if the lens is (a) a convex lens of focal length 20cm, and (b) a concave lens of focal length 16cm?
📋 Question Details
- Chapter
- Ray Optics
- Topic
- Focal length determination for lens and mirror
- Year
- 2016
- Shift
- 09 Apr Online
- Q Number
- Q22
- Type
- MCQ
- NCERT Ref
- Class 12 Physics Ch 9: Ray Optics
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