Conceptual Questions for Class 12 Physics Optical Instruments

Here we are providing conceptual questions for lass 12 physics chapter 9 Optical Instruments. Optical Instrument Topic is covered under class 12 physics chapter 9 Ray Optics and Optical Instruments. These questions are prepared by experts and are very useful from exam point of view. Students can practice these questions for scoring better marks in the exam. Students are suggested to go through each and every question for better understanding.

Q.1. How will the magnifying power of a refracting type astronomical telescope be affected on increasing for its eyepiece (i) the focal length and (ii) the aperture? Justify your answer.

Solution, (i) As m = f_o/f_e, so that magnifying decreases when focal length of eyepiece increases.

(ii) Magnifying power is not affected by the increase in. aperture of the eyepiece.

Q.2. What are the advantages of binocular vision?

Solution. The advantages of seeing an object with two eyes are:

1. The distance of the object can be correctly estimated.

2. The complete three-dimensional effect of the object can be obtained.

3. The two eyes give relief to one another after every fraction of second.

Q.3. How is the working of a telescope different from a microscope?

Solution. Working differences between a telescope and a microscope:

(ii) A telescope produces high resolution while a microscope produces high magnification.

(ii) The objective of a telescope forms the image of a very far off object at, or within, the focus of its eyepiece. The microscope does the same for a small object kept just beyond the focus of its objective.

(iii) The final image formed by a telescope is magnified relative to its size as seen by the unaided eye while the final image formed by a microscope is magnified relative to its absolute size.

(iv) The objective of a telescope has large focal length and large aperture while the corresponding quantities for a microscope have very small values.

(v) In a telescope, the distance between the objective and eyepiece is adjusted to focus the object at infinity. In a microscope the distance between the objective and eyepiece is fixed, the distance of the objective is changed to focus the object.

Q.4. Which two of the following lenses L₁, L₂and L₃ will you select as objective and eyepiece for constructing best possible (i) telescope (ii) microscope? Give reason to support your answer.

Lenses	Power (P)	Aperture (A)
L₁	3 D	8 cm
L₂	6 D	1 cm
L₃	10 D	1 cm

Solution. (i) Telescope. L₁ as objective and L₃ as eyepiece.

Reason. The objective should have large aperture and large focal length while the eyepiece should have small aperture and small focal length. Then the light gathering power and magnifying power will be larger.

(ii) Microscope, L₃ as objective and L₂ as eyepiece.

Reason. Both the lenses of the microscope should have short focal lengths and the focal length of the objective should be smaller than that of the eyepiece. Magnifying power will be larger for short focal lengths of objective and eyepiece.

Q.5. In a telescope, the objective has a large aperture while the eyepiece has a small aperture. Why?

Solution. The objective of large aperture has a large light gathering capacity and it forms bright images of even distant faint stars. Moreover, the large aperture of the objective increases the resolving power of the telescope.

The eyepiece of small aperture is taken so that entire light forming the final image may enter the small pupil of the eye and a brighter image is seen.

Q.6. Explain the basic differences between the construction and working of a telescope and a microscope.

Solution.

Construction differences:

Microscope	Telescope
1. Objective is of very short focal length and of short aperture. 2. Eyepiece is of short focal length (but f_e > f_o) and large aperture.	1. Objective is of large focal length and of large aperture. 2. Eyepiece is of short focal length and short aperture.

Working Differences:

Microscope	Telescope
1. Objective forms real and magnified image of an object kept just beyond its focus. 2. It produces linear magnification i.e., size of the image is larger than that of the object.	1. Objective forms image of the distant object at, or within, the focus of its eyepiece. 2. It produces angular magnification i.e., the image is nearer to the eye but the size does not increase.

Q.7. Which two main considerations are kept in mind while designing the ‘objective’ of an astronomical telescope?

Solution. Two main considerations with an astronomical telescope are: (i) its light gathering power and (ii) its resolving power.

The light gathering power depends on the area of the objective. With larger diameters, fainter objects can be observed. The resolving power, or the ability to observe two objects distinctly, which are very nearly in the same direction, also depends on the diameter of the objective.

Importance of conceptual questions for class 12 physics

Conceptual questions are of utmost importance in Class 12 Physics for several reasons. These questions focus on understanding the fundamental principles and concepts rather than just rote memorization of equations and formulas. Here are some reasons why conceptual questions are crucial in Class 12 Physics:

Deep understanding: Conceptual questions require students to grasp the underlying principles and theories behind physical phenomena. This leads to a deeper understanding of the subject, making it easier to apply the knowledge to various problem-solving scenarios.
Critical thinking: When students tackle conceptual questions, they are encouraged to think critically and analytically. These questions often involve complex scenarios that demand logical reasoning and creative thinking to arrive at the right answers.
Problem-solving skills: Conceptual questions challenge students to solve unfamiliar and intricate problems. As a result, their problem-solving skills are honed, preparing them to tackle more advanced scientific challenges in the future.
Application of concepts: By answering conceptual questions, students learn to apply theoretical concepts to practical situations. This bridges the gap between theory and real-world applications, fostering a holistic understanding of Physics.
Better exam preparation: Class 12 board exams and competitive entrance exams often include conceptual questions. Preparing for such questions not only improves performance in exams but also sets a strong foundation for further studies in physics-related fields.
Enhanced retention: Understanding concepts leads to better retention of knowledge. Unlike rote memorization, conceptual understanding stays with students for a long time, making it easier to build on that knowledge in the future.
Encouraging curiosity: Conceptual questions often pique students’ curiosity and encourage them to explore the subject further. This can spark an interest in Physics as a whole, leading to a lifelong passion for the subject.
Formulating connections: Conceptual questions help students make connections between different topics and subfields within Physics. This interconnected knowledge is essential for a comprehensive understanding of the subject.
Learning from mistakes: When students attempt conceptual questions, they may make mistakes. However, these mistakes provide valuable learning opportunities, as they highlight areas that need further clarification and understanding.
Building confidence: Successfully answering conceptual questions gives students a sense of accomplishment and boosts their confidence in their Physics abilities.

Conceptual Questions for Class 12 Physics Optical Instruments

Conceptual Questions for Class 12 Physics Optical Instruments

Importance of conceptual questions for class 12 physics

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