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

The NCERT Solutions for Class 12 Physics Chapter 9 – Ray Optics work towards guiding you in your practice and revisions of the chapter. These NCERT questions are based on the concepts from the chapter and provide an easy way of preparing for your CBSE exams. This chapter will introduce you to topics like Snell’s law, refraction of light, reflection of light, spherical mirrors, concave mirrors, convex mirrors, refractive index, normal etc.

NCERT Solutions for Class 12 Physics Chapter 9 – ‘Ray Optics and Optical Instruments’ consists of 1 exercise and 38 questions in total. This chapter has a wide range of questions which revolve around the theory, explanations, formulas, mathematical equations, examples and the numerical problems from the questions. There are short answer questions, descriptive questions, diagrammatic questions, analytical questions, observational questions, numerical problems and simple formula based questions.

The NCERT Solutions for Chapter 9 – Ray Optics by Instasolv, aims at ensuring that all your doubts are resolved at one place and you are not stuck in the chaos of finding various resources. Instasolv believes in eliminating all the unnecessary stress from your study curriculum and replacing it with a comfortable, productive and impactful learning environment. With our superior quality NCERT solutions and your efforts, nothing can stop you from scoring well in your exams.

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

Particle model of light

This chapter will introduce you to the concept of the particle model of light which was given by Newton. According to his model, light energy is concentrated in the form of very tiny particles which are termed as corpuscles. These corpuscles were believed to be massless and elastic particles. Through this theory, he drew out the fundamentals for reflection and refraction of light.

Reflection of light

This chapter will also teach you the fundamental concepts of the reflection of light and the rules which are followed during this phenomenon. These rules which are followed during the reflection of light through a reflecting surface are –

• The angle of reflection which lies between the reflected ray and the normal to the reflecting surface is equal in value to the angle of incidence which lies between the incident ray and the normal.
• The incident ray, the reflected ray and the normal to the reflecting surface at the point of incidence, all three lie at the same point.

Spherical mirrors

You will learn that spherical mirrors are of various kinds, the two major kinds being – the concave mirror and the convex mirror. The rays passing through both these mirrors are paraxial. In case of a convex mirror, the rays passing through it tend to diverge from the point F present on its principal axis whereas the rays passing through the concave mirror tend to converge.

Refraction

The chapter also deals with the concept of refraction. Unlike reflection where the beam of light is completely reflected, in case of refraction, the light is reflected back to the first medium and the rest of the light ray travels through the surface.

There are also laws of refraction given in the chapter which are known as Snell’s Laws –

• The incident ray, the refracted ray and the normal to the interface at the point of incidence are all located at the same plane.
• The ratio of the sine of the angle of incidence to the sine of the angle of refraction remains constant i.e  – sin i/ sin r = n21, here n21 is the refractive index of the second medium with respect to the first medium and it is a constant value.

## Exercise Discussion of NCERT Solutions for Class 12 Chapter 9 – Ray Optics and Optical Instruments

• The exercise begins with a simple question where the length of a candle kept in front of a concave mirror is given. The radius of curvature of the same mirror is also given and you are required to find the distance at which the screen must be placed to obtain a sharp image of the candle. The question also requires you to describe the characteristic nature of the image. This question requires the use of the very basic mirror formula to obtain the answer.
• Further, the chapter has questions like 9.11 where you are required to find the distance of distinct vision at infinity and the magnifying power of the microscope whose focal length has been given in the chapter. This question is a bit lengthy and required you to derive the answer using the lens formula which has been discussed in the chapter.
• The chapter also has exercises like 9.15 where you need to deduce equations according to the conditions that have been given in the question. These conditions need to be applied on the simple formulas from the chapter and you will easily have your answers with correct analysis and application.
• There is also a diagram-based question, question 9.17 where you are required to analyze the cross-section of a light pipe and answer the questions accordingly.
• Overall the exercises are a great way of grasping the essential points of the chapter and polishing your CBSE exam preparations.

## Benefits of NCERT Solutions for Class 12 Physics Chapter 9 – Ray Optics and Optical Instruments

The expert team at Instasolv has formulated all the NCERT solutions in a simplified language so that you can understand how to answer questions in the exam. We ensure that you develop a strong understanding of the chapter and all its major concepts. Each and every question has been tackled by our team step by step. We have also ensured that all the NCERT Solutions for Class 12 Physics Chapter 9 are as per the latest CBSE exam pattern and guidelines.

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