NCERT Solutions For Class 8 Science Chapter 10 - Light: Mirrors and Lenses

NCERT Solution for Class 8 Science Chapter 10 Download PDF

NCERT Solutions Class 8 Science Chapter 10 are properly structured to provide answers to all the questions in the textbook, and this is why this resource simplifies the gathering of various concepts necessary to students the most. The pdf format can be downloaded so that it can be studied and revised wherever, at any time.

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NCERT Solutions for Class 8 Science Chapter 10: Exercise Questions

NCERT Solutions of Class 8 Science Chapter 10 contain clear and step-by-step answers that enable the students to understand important concepts. The solutions aim at enhancing knowledge and honing examination preparation skills in problem-solving.

Q1: A light ray is incident on a mirror and gets reflected by it (Fig. 10.21). The angle made by the incident ray with the normal to the mirror is 40°. What is the angle made by the reflected ray with the mirror?

(i) 40°

(ii) 50°

(iii) 45°

(iv) 60°

Answer:

The angle made by the incident ray with the normal (angle of incidence) is 40°.

By the law of reflection, ∠i = ∠r, so, angle of reflection is also 40°.

The angle made by the reflected ray with the mirror is 90∘−40∘=50∘

So, the correct answer is (ii) 50°.

Q2: Fig. 10.22 shows three different situations where a light ray falls on a mirror:

(a) The light ray falls along the normal.

(b) The mirror is tilted, but the light ray still falls along the normal to the tilted surface.

(c) The mirror is tilted, and the light ray falls at an angle of 20° from the normal.

Draw the reflected ray in each case (Use a ruler and protractor for accurate drawing). What is the angle of reflection in each case?

Answer:

Case (i):

The light ray falls exactly along the normal (perpendicular to the surface).

The angle of incidence = 0°, so the angle of reflection = 0°.

The reflected ray goes straight back along the same path.

Case (ii):

The mirror is tilted, but the light ray again falls along the normal to the tilted surface.

The angle of incidence = 0°, so the angle of reflection = 0°.

The reflected ray goes straight back on itself.

Case (iii):

The mirror is tilted, and the light ray falls at a 20° angle from the normal.

Angle of incidence = 20°, so angle of reflection = 20°.

Draw the reflected ray on the other side of the normal, at 20°.

Q3: In Fig. 10.23, the cap of a sketch pen is placed in front of three types of mirrors.

Match each image with the correct mirror.

Answer:

Image (i): Smaller, erect, and covers a wide area → Convex mirror.

Image (ii): Enlarged, depending on distance → Concave mirror.

Image (iii): Same size, erect → Plane mirror.

Q4: In Fig. 10.24 the cap of a sketch pen is placed behind a convex lens, a concave lens, and a flat transparent glass piece — all at the same distance. Match each image with the correct type of lens or glass.

Answer:

Image (i): Larger than object (enlarged) → Convex lens.

Image (ii): Smaller than object (diminished) → Concave lens.

Image (iii): Same size as object → Flat transparent glass piece.

Q5: When the light is incident along the normal on the mirror, which of the following statements is true:

(i) Angle of incidence is 90°

(ii) Angle of incidence is 0°

(iii) Angle of reflection is 90°

(iv) No reflection of light takes place in this case

Answer:

(ii) Angle of incidence is 0°.

(The incident ray is perpendicular to the mirror, so the angle is zero.)

Q6: Three mirrors—plane, concave and convex are placed in Fig. 10.25. On the basis of the images of the graph sheet formed in the mirrors, identify the mirrors and write their names above the mirrors.

Answer:

• The mirror showing the same size grids: Plane mirror

• The mirror showing a smaller, wider grid: Convex mirror

• The mirror showing larger or possibly distorted grids, especially near the centre: Concave mirror

So, from left to right:

Convex mirror

Plane mirror

Concave mirror

Q7: In a museum, a woman walks towards a large convex mirror (Fig. 10.26). She will see that:

(i) Her erect image keeps decreasing in size.

(ii) Her inverted image keeps decreasing in size.

(iii) Her inverted image keeps increasing in size and eventually it becomes erect and magnified.

(iv) Her erect image keeps increasing in size.

Answer:

(i) Her erect image keeps decreasing in size.

Convex mirrors always show a small, erect image, and as you go closer, the image gets even smaller.

Q8: Hold a magnifying glass over text and identify the distance where you can see the text bigger than they are written. Now move it away from the text. What do you notice? Which type of lens is a magnifying glass?

Answer:

• As you bring the magnifying glass (convex lens) close to the text, you see the letters appear bigger (enlarged and erect) at a certain distance.

• If you move the lens too far, the image can become inverted or blurry.

• A magnifying glass uses a convex lens.

Q9: Match the entries in Column I with those in Column II.

Answer:

Q10: The following question is based on Assertion/Reason.

Assertion: Convex mirrors are preferred for observing the traffic behind us.

Reason: Convex mirrors provide a significantly larger view area than plane mirrors. Choose the correct option:

(i) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.

(ii) Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.

(iii) Assertion is correct but Reason is incorrect.

(iv) Both Assertion and Reason are incorrect.

Answer:

Convex mirrors show a wider field of view, so they are used as rear-view mirrors.

So, the correct answer is option (i) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.

Q11. In Fig. 10.27, note that O stands for object, M for mirror, and I for image. Which of the following statements is true?

(i) Figure (a) indicates a plane mirror and Figure (b) indicates a concave mirror.

(ii) Figure (a) indicates a convex mirror and Figure (b) indicates a concave mirror.

(iii) Figure (a) indicates a concave mirror and Figure (b) indicates a convex mirror.

(iv) Figure (a) indicates a plane mirror and Figure (b) indicates a convex mirror.

Answer:

(ii) Figure (a) indicates a convex mirror and Figure (b) indicates a concave mirror.

In a convex mirror, the image formed is always erect and diminished. In a concave mirror, the erect and enlarged image is formed behind the mirror

Q12. Place a pencil behind a transparent glass tumbler (Fig. 10.28a). Now fill the tumbler halfway with water (Fig. 10.28b). How does the pencil appear when viewed through the water? Explain why its shape appears changed.

Answer:

The pencil appears bent or broken at the water surface—this is called refraction.

Reason: The light rays change direction as they pass from water to air (because water and air have different densities), so the pencil seems displaced or bent at the surface.

NCERT Class 8 Science Chapter 10 Light: Mirrors and Lenses Overview

The NCERT solution for class 8 science chapter 10 deals with the amazing phenomena of mirrors and lenses. It starts off with spherical mirrors; that is, concave and convex ones, and describes how such mirrors may form different images depending on the position of the object. Enlarged or reduced, erect or inverted images could be produced by a concave mirror, while it is only a small, erect image that a convex mirror can always form.

Students will also be introduced to the laws of reflection, which state that the angle of incidence implies the angle of reflection and include the incident ray, reflected ray, and normal lying in the same plane. This is how the concave mirrors converge light rays and are utilised in torches, headlights, and dental tools. On the other hand, the convex mirrors diverge light rays for use in side-view mirrors and road safety mirrors.

The rest of this NCERT Class 8 science chapter, Light: Mirrors and Lenses, introduces us to the depth of lenses, which are transparent materials that refract light. A convex lens converges light and forms enlarged or reduced images, whereas a concave lens is always supposed to form smaller, erect images. Exercises magnificently demonstrate the use of lenses, which include using them in magnifying glasses, spectacles, cameras, or even in the human eye. This Light: Mirrors and Lenses chapter beautifully relates light to science and everyday life through simple experiments, turning the entire learning process into a fun-filled and practical experience.

Light: Mirrors and Lenses Class 8 Science Chapter 10: Topics

Chapter 10, Light: Mirrors and Lenses, of Class 8 Science opens a new world to the kids about optics. It describes the behaviour of light- its reflection and refraction, formation of image due to different surfaces, and also the uses of mirrors and lenses in our everyday life and in laboratory equipment. This chapter of the NCERT solution for class 8 science provides a solid path to realising and comprehending the physics of vision and optical equipment.

10.1 What Are Spherical Mirrors?

• Spherical mirrors are mirrors that have curved edges, and the reflecting surfaces belong to a sphere. Two types of them exist:
• Concave mirrors (inward-curved reflective surface) -focus light and can be found in things such as shaving mirrors, telescopes, and headlights.
• Convex mirrors (reflective surface extends outwards) -spread the light and are popularly applied as a rear mirror in automobiles.
• Both of them possess a pole (P), centre of curvature (C), principal axis and focus (F), and these contribute towards how they form an image.

10.2 What Are the Characteristics of Images Formed by Spherical Mirrors?

• The images formed depend on the location of the object relative to the focus and centre of curvature of the mirror. In the case of the concave mirrors, it may have either a real or virtual image which is either magnified, diminished and inverted, or upright. When dealing with convex mirrors, the image will always be virtual, erect and diminished. These characteristics can be understood with the help of ray diagram in various object positions.

10.3 What Are the Laws of Reflection?

• The reflection of light follows two basic laws:

1. Law of incidence and reflection – The angle of incidence equals the angle of reflection.
2. Plane of incidence – The incident ray, reflected ray, and normal to the mirror at the point of incidence lie in the same plane.

These laws are valid for both plane and spherical mirrors.

10.4 What Is a Lens?

• A lens is a clear optical instrument with one or more curved surfaces, which can converge or diverge light.

• Convex lens (thicker at the middle) -focuses light and it is capable of forming an image (real) or an image (virtual) depending on the position of the object being used.
• Concave lens (thinner in the centre) -this lens diverges light with the effect that it will produce virtual, erect, and reduced images all the time.
• There are numerous applications of lenses which include spectacles, microscopes, and cameras as well as magnifying glasses.

Approach to solve the questions of Class 8 Science Chapter 10

To make a good attempt at answering the questions in Class 8 Science Chapter 10 Light: Mirrors and Lenses, students are required to have a clear picture of the main concepts, which include the notions of reflection, refraction, image formation, and the distinction between concave and convex mirrors and lenses. Diagrams are very important; through the practice of ray diagrams, one is able to conceptualise how images are formed and to make correct responses to related questions. It is also recommended to revise definitions, formulas, and real-life applications because a lot of questions are concept-based. A combination of NCERT and exemplar problems helps develop an understanding and certainty in finding conceptual questions.

Chapter-wise NCERT Solutions of Class 8 Science

Chapter-wise NCERT Solutions Class 8 Science are very well organised answers to each of the questions of the latest NCERT book, each one solidifying concepts in the mind of the reader, so that he/she can not only have a good grasp of the topic but also be ready to tackle the exam. These solutions are resourceful in as much as they include every chapter in detail hence learning is more organized and easy to revise.