NCERT Solutions for Class 12 Physics, Chapter 9 - Ray Optics and Optical Instruments

In this chapter, you’ll study about Ray optics and Optical instruments in detail. Have you ever wondered why the sky looks blue most of the time and red during sunrise or sunset, or how a rainbow is formed or what makes the light scatter? Yes, all these are not only natural and beautiful phenomenon; there is a lot of science involved in these – the science of light, ray optics, reflection and refraction. In this chapter, you’ll study what reflection and refraction are all about and how these two concepts help in understanding the optical aspects of our world. You’ll also learn what is light, how it travels, functioning of the human eye,  reflection of light by spherical mirrors, total internal reflection, refraction at spherical surfaces and by lenses, power of a lens, refraction through a prism, detailed working mechanism of various optical instruments such as microscope and telescope along with diagrammatic representations and solved examples.

Thus, an in-depth study of Class 12 Physics NCERT Solutions Chapter 9 will give you a good understanding of significant aspects of Ray Optics and Optical Instruments.

Let’s take a look at topics and sub-topics of Class 12 Physics Chapter 9– Ray Optics and Optical Instruments

9.1 Introduction

9.2 Reflection of Light by Spherical Mirrors

9.2.1 Sign convention

9.2.2 Focal length of spherical mirrors

9.2.3 The mirror equation

9.3 Refraction

9.4 Total Internal Reflection

9.4.1 Total internal reflection in nature and its technological applications

9.5 Refraction at Spherical Surfaces and by Lenses

9.5.1 Refraction at a spherical surface

9.5.2 Refraction by a lens

9.5.3 Power of a lens

9.5.4 Combination of thin lenses in contact

9.6 Refraction through a Prism

9.7 Some Natural Phenomena due to Sunlight

9.7.1 The rainbow

9.7.2 Scattering of light

9.8 Optical Instruments

9.8.1 The microscope

9.8.2 Telescope

In Class 12 Physics Chapter 9, you will learn – 

Section 9.2 – In this section, you will study about the reflection of light by spherical mirrors, what is sign convention, the concept of the focal length of spherical mirrors and the mirror equation. You’ll also learn what is pole and optical centre, principal axis, Cartesian sign convention, paraxial, diagram showing focus of a concave and convex mirror and ray diagram for image formation by a concave mirror.

Section 9.3 – In this section, you’ll learn what is the refraction of light, what are the laws of refraction as proposed by Snell, what is refractive index, a diagram showing Refraction and reflection of light and more.

Section 9.4 – In this section, you’ll learn what internal reflection, total internal reflection, critical angle, total internal reflection mean; their nature and technological applications using mirage, diamond, prism and optical fibres.

Section 9.5 – In this section, you will study about refraction at a spherical surface separating two media, refraction by a lens, what is lens maker formula, thin lens formula, first focal point, second focal point, what is power of a lens, combination of thin lenses in contact, application of lenses in designing cameras, microscopes, telescopes and other optical instruments.

Section 9.6 – In this section, you’ll acquire knowledge about refraction through a prism, angle of deviation, diagram showing a ray of light passing through a triangular glass prism, and more.

Section 9.7 – In this section, you’ll come across some natural phenomena due to sunlight such as the rainbow and scattering of light. You’ll also study about chromatic aberration, refractive indices for different wavelengths; understand how a rainbow occurs and what Rayleigh scattering means.

Section 9.8 – In this section, you’ll learn about a number of optical devices and instruments that have been designed utilising reflecting and refracting properties of mirrors, lenses and prisms such as the periscope, kaleidoscope, binoculars, telescopes, microscopes and most importantly, the human eye.  You’ll also learn about the principles of working of the microscope and the telescope in detail.

In this chapter, you are provided with several examples with their solutions for clear understanding about Ray Optics and Optical Instruments. To know more about NCERT Solutions for Class 12 Physics Chapter 9, you should explore the exercises mentioned in this chapter. You can also download the NCERT Solutions for Class 12 Physics Chapter 9 PDF, solved by our science experts.