# CBSE Class 10 Important Questions on Science Chapter 10 - Light Reflection and Refraction 2022-23 (2023)

The following list of important topics covered under the chapter on Light Reflection and Refraction has been provided for students so that they can take a glance at the major concepts and read them through before diving into the important questions.

• Reflection of Light

• Spherical Mirrors

• Image Formation by Spherical Mirrors

• Sign Convention for Spherical Mirrors

• Mirror Formula and Magnification

• Refraction of Light

• Refraction through a Rectangular Glass Slab

• Refractive Index

• Refraction by Spherical Lenses

• Image Formation by Lenses and Their Ray Diagrams

• Sign Convention for Spherical Lenses

• Lens Formula and Magnification

• Power of a Lens

## Study Important Questions for Class 10 Science Chapter 10 - Light Reflection and Refraction

1. A convex lens has a focal length of $10$ cm. At what distance from the lens should the object be placed so that it forms a real and inverted image $20$ cm. away from the lens? What would be the size of the image formed if the object is $2$ cm high? With the help of a ray, the diagram shows the formation of the image by the lens in this case?

Ans: Given, the focal length of the convex lens,

$\Rightarrow f=+10$ cm

Also, given the image formed is real and inverted with the image distance as $20$ cm.

$\Rightarrow v=+20$ cm

From the lens formula, we have:

$\Rightarrow \dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}$

$\Rightarrow \dfrac{1}{10}=\dfrac{1}{20}-\dfrac{1}{u}$

$\Rightarrow \dfrac{1}{u}=\dfrac{1}{20}-\dfrac{1}{10}$

$\Rightarrow \dfrac{1}{u}=\dfrac{-1}{20}$

(Video) Light Reflection & Refraction - Most Important Questions | Class 10 Physics Chapter 10 (LIVE)2022-23

$\Rightarrow u=-20$ cm.

$\therefore$ The object is placed at a distance of $20$ cm.

Magnification is given as,

$\Rightarrow m=-\dfrac{v}{u}$

$\Rightarrow m=-\dfrac{20}{\left( -20 \right)}$

$\Rightarrow m=+1$

Also, magnification is given by, $m=\dfrac{Height\text{ of the image}}{Height\text{ of the object}}$.

$\therefore m=\dfrac{Height\text{ of the image}}{2}$

$\Rightarrow 1=\dfrac{Height\text{ of the image}}{2}$

$\Rightarrow Height\text{ of the image}=2$ cm.

Thus, the image is of the same size as that of the object and it is real and inverted.

The ray diagram representing the formation of the image by the lens in this case is: It is observed that the image is formed at $2{F_2}$ with the object placed at $2{F_1}$.

2. Draw a ray diagram to show the use of a convex lens for the formation of images having the following characteristics.

a. Real & inverted and diminished

Ans: A ray diagram representing a real & inverted and diminished image is given below. When the object is kept outside $2{F_1}$ (Centre), we get a real, inverted, and diminished image between ${F_2}$ and $2{F_2}$.

b. Virtual, erect & magnified.

Ans: A ray diagram representing a virtual, erect, and magnified image is given below. (Video) Class 10 Physics | Light Reflection & Refraction - Most Important Short Ans Questions (2022-23) LIVE

When the object is kept at a distance less than ${F_1}$ (Focus), we get a virtual, erect, and magnified image outside $2{F_1}$ (Centre).

3. A convex lens forms a real and inverted image of a needle at a distance of $50$ cm. from it. Where is the needle placed in front of the convex lens if the image is equal to the size of objects? Also, find the power of the lens.

Ans: Given, the image is real and inverted at a distance of $50$ cm.

$\Rightarrow v=+50$ cm

Also given, Height of image $=$ Height of object

We know, magnification is given as,

$\Rightarrow m=-\dfrac{v}{u}$

Also, magnification is given by, $m=\dfrac{Height\text{ of the image}}{Height\text{ of the object}}$.

$\therefore -\dfrac{v}{u}=\dfrac{Height\text{ of the image}}{Height\text{ of the object}}$

Since, Height of image $=$ Height of object and $v=+50$ cm

$\Rightarrow -\dfrac{50}{u}=1$

$\Rightarrow u=-50$ cm

From the lens formula, we have:

$\Rightarrow \dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}$

$\Rightarrow \dfrac{1}{f}=\dfrac{1}{50}-\dfrac{1}{-50}$

$\Rightarrow f=25$ cm

$\Rightarrow f=0.25$ m

The power of a lens is given by,

$\Rightarrow P=\dfrac{1}{f}$

$\Rightarrow P=\dfrac{1}{0.25}$ m

$\Rightarrow P=+4$ D

4. One-half of a convex lens is covered with black paper. Will this lens produce a complete image of the object? Verify your answers experimentally. Explain your observations.

Ans: If we cover one-half of a convex lens with black paper it is observed that it produces a complete image of the object.

Representing the given situation with a ray diagram. (Video) CBSE 2023 Most Important 3 Marks Questions Class 10 Science |Ch-10 Light Reflection & Refraction |

Suppose we take a convex lens that is half-covered with black paper. On one side of the lens, we keep a burning candle and a screen on the other side of the lens.

Adjust the position of the burning candle such that its image is formed on the screen placed on the other side of the lens.

We get a full image of the burning candle on the screen.

Thus, from the above observation, we conclude that the formation of an image does not depend on the length of the lens, but the brightness of the image formed on the screen depends since the number of rays passing through the lens gets reduced on covering half the lens with black paper.

5. An object $5$ cm in length is held $25$ cm away from a converging lens of focal length $10$ cm. Draw the ray diagram and find the position, size, and nature of the image formed.

Ans: Given focal length of the lens, $f=+10$ cm.

Object distance from the converging lens is given to be $25$ cm and the height of the object ($ho$) is given to be $5$ cm.

Thus,

$\Rightarrow u=-25$ cm

$\Rightarrow ho=5$ cm

From the lens formula, we have:

$\Rightarrow \dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}$

$\Rightarrow \dfrac{1}{10}=\dfrac{1}{v}-\dfrac{1}{-25}$

$\Rightarrow \dfrac{1}{v}=\dfrac{1}{25}-\dfrac{1}{10}$

$\Rightarrow v=\dfrac{50}{3}$ cm

$\Rightarrow v=16.7$ cm

Thus, we conclude that the image formed is real and inverted and is formed at a distance of $16.7$ cm on the other side of the lens.

We know, magnification is given as,

$\Rightarrow m=-\dfrac{v}{u}$

Also, magnification is given by, $m=\dfrac{Height\text{ of the image}}{Height\text{ of the object}}=\dfrac{hi}{ho}$.

$\therefore -\dfrac{v}{u}=\dfrac{hi}{ho}$

$\Rightarrow \dfrac{16.7}{-25}=\dfrac{hi}{5}$

$\Rightarrow hi=-\dfrac{10}{3}$ cm

Hence, the image is diminished.

The ray diagram representing the above situation is drawn below.

(Video) Light Reflection and Refraction Important Questions | Class 10 Science Chapter 10 Board 2023 6. A convex lens of focal length $15$ cm formed an image $10$ cm from the lens. How far is the object placed from the lens? Draw the ray diagram.

Ans: Given focal length of the lens, $f=15$ cm.

Image distance from the converging lens is given to be $10$ cm.

Thus,

$\Rightarrow v=-10$ cm

We observe that the image distance is less than the focal length, hence the image formed would be virtual and erect.

From the lens formula, we have:

$\Rightarrow \dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}$

$\Rightarrow \dfrac{1}{15}=\dfrac{1}{-10}-\dfrac{1}{u}$

$\Rightarrow \dfrac{1}{u}=-\dfrac{1}{10}-\dfrac{1}{15}$

$\Rightarrow u=-6$ cm

The ray diagram representing the above situation is drawn below. ## Light: Reflection and Refraction - Important Questions and Solutions Summary

light rays, mirrors, lenses, prisms, etc., is the advanced version of what you As mentioned earlier, the chapter related to light, reflection, and refraction of have studied in the previous classes. In Class 10, you will have to focus on the theoretical part, as well as, the use of these theories to answer questions.

Class 10 Light Reflection and Refraction Important Questions have been developed by the expert teachers to provide a strong idea of how questions are set in the exams. All these questions are developed to define how theoretical concepts are used to solve conceptual problems. You will gain a better insight into the chapters and strengthen your foundation accordingly.

### Benefits of Studying the CBSE Class 10 Important Questions on Science Chapter 10 - Light Reflection and Refraction

The Important Questions for Class 10 Light Reflection and Refraction have been developed based on the basic and advanced concepts you have learned in your science textbook. Let us check the benefits of studying these questions first.

### Thinking Out of the Box

The Important Questions of Light Reflection and Refraction Class 10 is the ultimate suggestion for the upcoming board exam. You can study these questions, prepare their answers on your own, and compare them with the solution provided. This will help you to understand how efficiently you have studied the chapter. Light Class 10 Important Questions have been developed to help you think out of the box. In most cases, the thoughts of the students remain stuck in the exercises of the textbook. These questions will help them think out of the box and challenge their intellect.

### Getting to Know Possible Important Questions of Chapter 10 Class 10 Science

By studying Class 10th Science Chapter 10 Important Questions, you will get to know possible questions that might come in the board exams. All these questions are developed by experienced science teachers. They are well-aware of the type of questions asked in the CBSE exam. Hence, studying these questions will help you learn about different modes and patterns.

### Making Concepts Easier to Understand

The Important Questions for Class 10 Science Light Reflection and Refraction have simple explanations. All the concepts in this chapter will be exceptionally simplified and utilized to answer these important questions. Hence, the students will get another way to learn how to use the textbook concepts to solve challenging questions in the exams.

The Ch 10 Science Class 10 Important Questions will also come with a proper solution. The solutions will have the perfect answers to all these important questions. You will get another set of questions and answers to follow and find out the best approaches to score well in the exams. These approaches are simplified and designed by following the CBSE guidelines.

(Video) Class 10 Physics | Light Reflection and Refraction - Important Long Answer Questions (2022-23) LIVE

### Mastering Solving Numerical Questions

This chapter poses a challenge in the form of numerical questions related to mirrors and lenses. These problems are based on a set of formulas related to the focal distance, object distance, and image distance of lenses and mirrors. By using Class 10 Science Chapter 10 Important Questions and Solutions, you can master using the formula in different aspects without committing mistakes.

You can download Chapter 10 Science Class 10 Important Questions and solutions in PDF format and study them offline. Get this extra set of questions and use them as a reference to clear your concepts of this crucial chapter.

## Important Related Links for CBSE Class 10 Science

 CBSE Class 10 Science Study Materials CBSE Class 10 Science NCERT Solutions CBSE Class 10 Science Revision Notes CBSE Class 10 Science Sample Papers CBSE Class 10 Science NCERT Exemplar Solutions CBSE Class 10 Science Previous Year Question Papers

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