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# Unit 1: Light – reflection & refraction (Hindi)

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## About this unit

When light travels from one medium to another (like air to glass, or glass to water), it does three things. Some of it bounces off, some of it goes through, and the rest of it is absorbed. In this chapter, we will explore the first two. We will explore what rules govern them, their technical names and then apply these rules to study the beautiful world of curved mirrors and lenses.

We see light bouncing all around us. It makes us see most of the things. In this lesson, we will explore the rule that this 'bouncing' of light obeys and talk about plane mirrors.

We have experience and intuition for flat mirrors. But if we slightly curve these mirrors, a whole new world opens up. In this lesson we will explore the concave and convex mirrors and their applications.

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### Practice

- Applications of concave and convex mirrorsGet 3 of 4 questions to level up!

Let's learn how to construct images, when an object is kept in front of curved mirrors, using ray diagrams.

### Practice

- Ray diagramsGet 3 of 4 questions to level up!
- Ray diagrams and curved mirrorsGet 3 of 4 questions to level up!

It's possible to address whether a mirror is concave or convex, whether an object is in front or behind the mirror, whether an image is real or virtual, with just positive and negative signs. Let's explore how in this lesson

### Practice

- Sign conventionGet 3 of 4 questions to level up!

Level up on the above skills and collect up to 320 Mastery points

let's see if we can figure out where an image would be, given where an object is kept in front of a curved mirror. In effect, we will end up deriving the famous mirror formula.

Let's explore how to use the mirror formula to locate image positions when objects are kept in front of convex and concave mirrors.

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### Practice

- Using the mirror formulaGet 3 of 4 questions to level up!
- Using the magnification formula for mirrorsGet 3 of 4 questions to level up!
- Nature and size of images from magnificationGet 3 of 4 questions to level up!
- Concave and convex mirrorsGet 3 of 4 questions to level up!

Level up on the above skills and collect up to 320 Mastery points

You may have seen that a straw, immersed in a glass of water, appears bent. It's actually the light, coming from the straw, that's bent. Light bends when it changes medium. It's a big deal because if it didn't, our eyes wouldn't work. So let's explore this bending of light in this lesson.

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### Practice

- Snell's law of refractionGet 3 of 3 questions to level up!

In this lesson, we will clarify the difference between absolute & relative refractive index. We will also see how to connect them.

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### Practice

- Refractive index and the speed of lightGet 3 of 4 questions to level up!
- Connection between relative and absolute refractive indicesGet 5 of 7 questions to level up!

Let's explore how to construct images, when objects are kept in front of a lens, by drawing ray diagrams.

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### Practice

- Image formation in spherical lensesGet 3 of 4 questions to level up!
- Paths of light rays through spherical lensesGet 3 of 4 questions to level up!

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Given the object location and focal length of a lens, let's figure out exactly where the image would be. We will be deriving the lens formula & magnification formula for lenses.

Let's explore how to use the lens formula to figure out where images are and how big they get when some objects are kept in front of lenses.

### Learn

### Practice

- Using magnification formula for lensesGet 3 of 4 questions to level up!
- Using the lens formulaGet 3 of 4 questions to level up!
- Convex and concave lensesGet 3 of 4 questions to level up!

You may have heard about power related to your eye after a typical eye exam. Let's explore what this 'power' is and why define them that way.

### Practice

- Power of lensGet 3 of 4 questions to level up!

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