Q22.An object 2.4 m in front of a lens forms a sharp image on a film 12 cm behind the lens. A glass plate 1 cm thick, of refractive index 1.50 is interposed between lens and film with its plane faces parallel to film. At what distance (from lens) should object be shifted to be in sharp focus on film? (1) 7.2 m (2) 2.4 m (3) 3.2 m (4) 5.6 m
What This Question Tests
This problem requires applying the lens formula to find the focal length, calculating the apparent shift caused by a glass slab placed in the image path, and then using the shifted image position to find the new object distance.
Concepts Tested
Formulas Used
1/f = 1/v - 1/u
Shift = t(1 - 1/ฮผ)
๐ NCERT Sections This Tests
9.19 โ A Screen Is Placed 90Cm From An Object. The Image Of The Object On
Physics Class 12 ยท 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.
9.8 โ A Beam Of Light Converges At A Point P. Now A Lens Is Placed In The
Physics Class 12 ยท 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?
9.3 โ A Tank Is Filled With Water To A Height Of 12.5 Cm. The Apparent
Physics Class 12 ยท Chapter 9
9.3 A tank is filled with water to a height of 12.5 cm. The apparent depth of a needle lying at the bottom of the tank is measured by a microscope to be 9.4 cm. What is the refractive index of water? If water is replaced by a liquid of refractive index 1.63 up to the same height, by what distance would the microscope have to be moved to focus on the needle again?
๐ Question Details
- Chapter
- Ray Optics
- Topic
- Lens formula and optical shift
- Year
- 2012
- Shift
- Offline
- Q Number
- Q22
- Type
- Numerical
- NCERT Ref
- Class 12 Physics Ch 9: Ray Optics and Optical Instruments
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