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# NCERT Exemplar Class 12 Physics Chapter 9 Solutions: Ray Optics and Optical Instruments

NCERT Exemplar Class 12 Physics Solutions Chapter 9 – Ray Optics and Optical Instruments help you to revise the complete syllabus and score more marks in Class 12 Board Exams. To give you a gist, this chapter of NCERT Exemplar Class 12 Physics explain Refraction, Incident Ray and Refracted, Laws of Reflection and Refraction, Refractive Index, Convex and Concave Mirrors, Transparent and Translucent Medium, Focal plane, Focal length, and Principal focus.

NCERT Exemplar Solutions for Chapter – Ray Optics and Optical Instruments have a total of 32 questions that are divided into 5 sections touching all the topics of ray optics and optical instruments. The questions are of various kinds which help you get a complete revision with the help of short and long type questions, objective type questions, and MCQs kind of questions.

Instasolv has created solutions to various NCERT Exemplar Solutions in unique and smooth steps that you can learn easily. By following the strategies of the professionals at Instasolv, you can score well in the CBSE exams and have an edge while taking various competitive exams like JEE.

## Important Topics for NCERT Exemplar Class 12 Physics Solutions Chapter 9 – Ray Optics and Optical Instruments

• Reflection: When light is incident on a surface, it’s sent back by the surface within the same medium through which it had come. This phenomenon is termed ‘reflection of light’ by the surface.
• Laws of Reflection: The reflection at a plane surface always takes place following the subsequent two laws:
(i) the incident ray, the reflected ray and normal to surface at the purpose of incidence all lay on the identical plane.
(ii) The angle of incidence i is always equal to the angle of reflection r, i. e.,

Reflection of Light from Spherical Mirror:
The reflection at the spherical mirror also takes place following the laws of reflection.

• Focal Length of a Spherical Mirror:
a) It is the distance between the focus and the pole of the mirror, Represented by f.
b) The focal length of a concave mirror is always negative and the convex mirror is positive.
c) The focal length of a mirror is, f = R/2.
• Principal Axis of the Mirror: The line joining the pole and also the centre of curvature of spherical mirror extended on either side
• Refraction: It is the change within the path of light because it passes obliquely from one transparent medium to another.
• Laws of Refraction: when an incident ray, reflected ray and the normal ray to the interface of any two given mediums; all lie in the same plane.
• Apparent Depth of a Liquid: when an object is placed at the bottom of a transparent medium and observed from the above, it will appear as higher than the actual level.
The refractive index u, in this case, is:
Refractive index of the medium,  u =

• Refraction through a Thin Lens (Lens maker’s formula): considering R1 and R2 as radii of curvature of first and second refracting surfaces of a thin lens of focal length f, then the lens-makers formula is
Here, the lens is surrounded by air i.e  u1 =1   and  u2 = u , then

• Refraction Through Prism: A ray of monochromatic light when refracted by a prism, the deviation  produced by the prism is

Where i = angle of incidence
e = angle of emergence

A = angle of the prism

• Dispersion: It is the separation of white light into constituent colours
• The pattern of the coloured bands obtained on the screen is called a spectrum.

• Angular dispersion: The splitting of two extreme colours (violet and red) under a spectrum of light is called the angular dispersion.

• Dispersive Power: It is defined as the ratio of the angular dispersion to the mean deviation.

• Optical Instruments: Those optical tools which assist humans to observe profoundly amplified pictures of minor articles, for point by point assessment and in watching exceptionally far items whether earthbound or cosmic.
• Human Eye: It is said to be a natural optical instrument where light enters through a curved front surface i.e., the cornea passes through the pupil.
Microscope: it is an optical instrument that empowers us to see a small object.
Telescope: It is an optical device that empowers us to see distant objects.

## Discussion of Exercises of NCERT Exemplar Solutions for Chapter 9

1. The first set of questions is MCQs (part 1) with 11 questions. This will test your knowledge of different types of laws related to optic rays.
2. The second set of questions is MCQS (part 2) with 5 questions. This will test your understanding of optical instruments and their uses.
3. The third set of questions is a very short answer type question with 5 questions. They are a mixture of different important topics including focal length, the position of final image formed by a lens, apparent depth of the liquid, glass prism, etc.
4. The fourth set of questions is short answer type questions with 6 questions. These are numerical based questions that will help you to understand the application of different formulas as per given situations.
5. The fifth set of questions is long answer type questions with 5 questions. These are the theoretical questions that help you to understand the working of different optical instruments through ray diagrams.
6. The NCERT Exemplar Class 12 Physics Solutions Chapter 9 is created by instasolv subject experts based on the latest syllabus. This will help you achieve the highest marks board exams.

## Why Use NCERT Exemplar Class 12 Physics Solutions for Chapter 9 by Instasolv?

NCERT Exemplar Class 12 Solutions Chapter 9 – Ray Optics and Optical Instruments by Instasolv experts incorporates all the significant subjects with point by point clarification that plans to assist students with understanding the ideas better. Experiencing the arrangements given on this page will assist you in knowing how to approach and take care of the issues.

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