Question:
The magnifying power of a telescope is $9.$ When it is adjusted for parallel rays the distance between the objective and eyepiece is $20\, cm.$ The focal length of lenses are
The magnifying power of a telescope is $9.$ When it is adjusted for parallel rays the distance between the objective and eyepiece is $20\, cm.$ The focal length of lenses are
Updated On: Jul 13, 2024
- 10 cm, 10 cm
- 15 cm, 5 cm
- 18 cm, 2 cm
- 11 cm, 9 cm
Hide Solution
Verified By Collegedunia
The Correct Option is C
Solution and Explanation
Magnifying power, m = $\frac{f_{o}}{f_{e}} = 9$...(i)
where and are the focal lengths of the objective
and eyepiece respectively
Also, $f_{o} +f_{e} = 20\, cm$...(ii)
On solving (i) and (ii), we get
$f_{o} = 18\, cm,\, f_{e} = 2\, cm$
where and are the focal lengths of the objective
and eyepiece respectively
Also, $f_{o} +f_{e} = 20\, cm$...(ii)
On solving (i) and (ii), we get
$f_{o} = 18\, cm,\, f_{e} = 2\, cm$
Was this answer helpful?
0
0
Top Questions on Optical Instruments
- A concave mirror has a focal length of 20 cm. An object is placed 60 cm in front of the mirror. Find the image distance.
- MHT CET - 2025
- Physics
- Optical Instruments
- A microscope has an objective of focal length \(f_o = 2\) cm and an eyepiece of focal length \(f_e = 4\) cm. The tube length of the microscope is \(L = 40\) cm. If the distance of distinct vision of eye is \(D = 25\) cm, the magnification in the microscope is:
- NEET (UG) - 2025
- Physics
- Optical Instruments
- The eye defect astigmatism can be corrected by using a
- KEAM - 2025
- Physics
- Optical Instruments
- The clarity of the image formed on the retina of the eye depends on the ____
- MHT CET - 2025
- Physics
- Optical Instruments
- In normal adjustment, for a refracting telescope, the distance between the objective and eyepiece lens is 1.00 m. If the magnifying power of the telescope is 19, find the focal length of the objective and the eyepiece lens.
- CBSE CLASS XII - 2024
- Physics
- Optical Instruments
View More Questions
Questions Asked in NEET exam
The current passing through the battery in the given circuit, is:
- NEET (UG) - 2025
- Current electricity
A bob of heavy mass \(m\) is suspended by a light string of length \(l\). The bob is given a horizontal velocity \(v_0\) as shown in figure. If the string gets slack at some point P making an angle \( \theta \) from the horizontal, the ratio of the speed \(v\) of the bob at point P to its initial speed \(v_0\) is :
- NEET (UG) - 2025
- Pendulums
- Two cities X and Y are connected by a regular bus service with a bus leaving in either direction every T min. A girl is driving scooty with a speed of 60 km/h in the direction X to Y. She notices that a bus goes past her every 30 minutes in the direction of her motion, and every 10 minutes in the opposite direction. Choose the correct option for the period T of the bus service and the speed (assumed constant) of the buses.
- NEET (UG) - 2025
- Relative Velocity
- The intensity of transmitted light when a polaroid sheet, placed between two crossed polaroids at \(22.5^\circ\) from the polarization axis of one of the polaroids (\(I_0\) is the intensity of polarised light after passing through the first polaroid):
- NEET (UG) - 2025
- Polarization
A full wave rectifier circuit with diodes (\(D_1\)) and (\(D_2\)) is shown in the figure. If input supply voltage \(V_{in} = 220 \sin(100 \pi t)\) volt, then at \(t = 15\) msec:
- NEET (UG) - 2025
- Semiconductor Diode
View More Questions
Concepts Used:
Optical instruments
A device that processes light waves (or photons), either to enhance an image for viewing or to analyze and determine its characteristic properties is called an optical instrument (or "optic" for short).
Applications of Optical Instruments:
- Microscope - It is one of the most extensively used optical instruments comprised of only one lens or combination of the lenses for magnifying and inspecting bodies that are too small to be seen in detail by clear eyes. Earlier microscopes had only one lens, and are, therefore, called simple microscopes, but the present microscopes are accessible with at least two lenses and thereby, termed a compound microscope.
- Telescope - It is another remarkable optical instrument. It makes distant objects emerge nearer by using an arrangement of lenses or lenses and curved mirrors that is used to observe the objects by absorption, emission, and reflection of their electromagnetic radiation to furnish a magnified image. As they are used to view objects that are far away, they include at least two lenses.