Doubt Banner

NCERT Books Class 12 Physics Chapter 9- Ray Optics and Optical Instruments

Safalta Expert Published by: Noor Fatima Updated Sat, 25 Jun 2022 12:09 PM IST

Highlights

Here is the information about NCERT Books Class 12 Physics Chapter 9. You can give a read to this blog and get PDFs of the subject. 
 

NCERT Books Class 12 Physics Chapter 9- Ray Optics and Optical Instruments is accessible here for download purposes. You can download the PDF for and learn from the book anytime you want. Students who are studying in Class 12 and candidates who are preparing for competitive exams can download the PDF for NCERT Books Class 12 Physics Chapter 9- Ray Optics and Optical Instruments to learn from the reading material.  

Taking these course books as a reference can be really helpful to prepare for any sought exam. You can keep the digital form of the book handy and learn from it without any time constraints.

At safalta, you can access FREE E-BOOKS. These books are not just free of cost, but they are also packed with ample knowledge and information related to your studies.

We also provide FREE MOCK PAPERS, which can help you test your own yourself. These papers can help you prepare for your exams in a better way.

Here, you can learn the NCERT Books Class 12 Physics Chapter 9- Ray Optics and Optical Instruments. Moreover, you can get the links for other chapters to download the links. 

The Chapter Goes Like This-


INTRODUCTION

Nature has endowed the human eye (retina) with the sensitivity to detect electromagnetic waves within a small range of the electromagnetic spectrum.

Free Demo Classes

Register here for Free Demo Classes

Please fill the name
Please enter only 10 digit mobile number
Please select course
Please fill the email
Electromagnetic radiation belonging to this region of the spectrum (wavelength of about 400 nm to 750 nm) is called light. It is mainly through light and the sense of vision that we know and interpret the world around us.

There are two things that we can intuitively mention about light from common experience. First, that it travels with enormous speed and second, that it travels in a straight line. It took some time for people to realise that the speed of light is finite and measurable. Its presently accepted value in vacuum is c = 2.99792458 × 108 m s–1. For many purposes, it suffices to take c = 3 × 108 m s–1. The speed of light in vacuum is the highest speed attainable in nature.

The intuitive notion that light travels in a straight line seems to contradict what we have learnt in Chapter 8, that light is an electromagnetic wave of wavelength belonging to the visible part of the spectrum. How to reconcile the two facts? The answer is that the wavelength of light is very small compared to the size of ordinary objects that we encounter commonly (generally of the order of a few cm or larger). In this situation, as you will learn in Chapter 10, a light wave can be considered to travel from one point to another, along a straight line joining them. The path is called a ray of light, and a bundle of such rays constitutes a beam of light.

In this chapter, we consider the phenomena of reflection, refraction and dispersion of light, using the ray picture of light. Using the basic laws of reflection and refraction, we shall study the image formation by plane and spherical reflecting and refracting surfaces. We then go on to describe the construction and working of some important optical instruments, including the human eye.


REFLECTION OF LIGHT BY SPHERICAL MIRRORS

We are familiar with the laws of reflection. The angle of reflection (i.e., the angle between reflected ray and the normal to the reflecting surface or the mirror) equals the angle of incidence (angle between incident ray and the normal). Also that the incident ray, reflected ray and the normal to the reflecting surface at the point of incidence lie in the same plane (Fig. 9.1). These laws are valid at each point on any reflecting surface whether plane or curved. However, we shall restrict our discussion to the special case of curved surfaces, that is, spherical surfaces. The normal in this case is to be taken as normal to the tangent to surface at the point of incidence. That is, the normal is along the radius, the line joining the centre of curvature of the mirror to the point of incidence.

We have already studied that the geometric centre of a spherical mirror is called its pole while that of a spherical lens is called its optical centre. The line joining the pole and the centre of curvature of the spherical mirror is known as the principal axis. In the case of spherical lenses, the principal axis is the line joining the optical centre with its principal focus as you will see later.


Sign convention

To derive the relevant formulae for reflection by spherical mirrors and refraction by spherical lenses, we must first adopt a sign convention for measuring distances. In this book, we shall follow the Cartesian sign convention. According to this convention, all distances are measured from the pole of the mirror or the optical centre of the lens. The distances measured in the same direction as the incident light are taken as positive and those measured in the direction opposite to the direction of incident light are taken as negative (Fig. 9.2). The heights measured upwards with respect to x-axis and normal to the principal axis (x-axis) of the mirror/ lens are taken as positive (Fig. 9.2). The heights measured downwards are taken as negative.

With a common accepted convention, it turns out that a single formula for spherical mirrors and a single formula for spherical lenses can handle all different cases.

Get through the entire chapter with the help of PDF (link) given below. 
 
NCERT Books Class 12 Physics Chapter 9- Ray Optics and Optical Instruments- PDF Download

Chapter 9- Ray Optics and Optical Instruments

अध्याय 9 किरण प्रकाशिकी एवं प्रकाशिक यंत्रा

 

Where can you download NCERT Books Class 12 Physics Chapter 9 PDF?

Candidates can download NCERT Books Class 12 Physics Chapter 9- Ray Optics and Optical Instruments PDF for free on our page. Links are given below.

Chapter 9- Ray Optics and Optical Instruments

अध्याय 9 किरण प्रकाशिकी एवं प्रकाशिक यंत्रा

Why is NCERT Books Class 12 Physics the best study material?

The book can also help in clarifying doubts. Other benefits of studying from the NCERT Books Class 12 Physics are-
  • Students gain profound knowledge about Physics through the NCERT Books Class 12 Physics
  • The course books contain pictures that can help students in better understanding of the chapters
  • These books can help students in self-study

Why is NCERT Books Class 12 Physics so recommended for board exams?

Almost all the questions that appear in board exams are from NCERT Books Class 12 Science. Moreover, a team of professional teachers drafts these books, which become a reliable source of study for students.
 

Are CBSE Books for Class 12 Physics important from an examination perspective?

The chapters in CBSE Books for Class 12 Physics are vital for board exams and higher classes. Students should read the chapter given in the CBSE books for Class 12 Science. These stories and practice questions can help gain excellent marks.

To get outstanding marks, we provide mock test papers that can help gear-up your preparations for exams. Additionally, you can also download e-books to get yourself prepared even in a better way.
 
 

Free E Books