NCERT Solutions for Class 8 Science Chapter 16 Light

NCERT Solutions for Class 8 Science Chapter 16 - Light

Welcome to the Chapter 16 - Light, Class 8 Science NCERT Solutions page. Here, we provide detailed question answers for Chapter 16 - Light. The page is designed to help students gain a thorough understanding of the concepts related to natural resources, their classification, and sustainable development.

Our solutions explain each answer in a simple and comprehensive way, making it easier for students to grasp key topics Light and excel in their exams. By going through these Light question answers, you can strengthen your foundation and improve your performance in Class 8 Science. Whether you’re revising or preparing for tests, this chapter-wise guide will serve as an invaluable resource.

Exercise 1

Q 1:

Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room. Explain.

We cannot see objects in the dark room due to the absence of the light. But we can see the objects outside the room due to the presence of light outside the room. The light falls on the objects and gets reflected. These reflected rays then reaches to out eyes which enables us to see the objects.

Q 10:

Draw a labeled sketch of the human eye.

Q 11:

Gurmit wanted to perform Activity 16.8 using a laser torch. Her teacher advised her not to do so. Can you explain the basis of the teachers advise?

Gurmit’s teacher advised her not to do so because laser torch can injure the retina of her friends and she may loss her eye sight permanently or temporarily. The intensity of laser light is very high.

Q 12:

Explain how you can take care of your eyes.

We should take care of our eyes properly. If there is any problem in the eyes then we should consult eye specialist.

We should not read in the too much light or too little light.
Never see sun or other powerful source of light directly.
We should not rub the eyes if the dust or some other contaminants get falls into the eyes.
Always read and write by keeping books at a normal distance for a vision.

Q 13:

What is the angle of incidence of a ray if the reflected ray is at an angle of 90° to the incident ray?

∠i + ∠r = 90◦

But, by the first law of reflection;

∠i = ∠r

∠i + ∠r = 90◦

∠i + ∠i = 90◦

2∠i = 90◦

∠i = 90◦ = 45◦ 2

Q 14:

How many images of a candle will be formed if it is placed between two parallel plane mirrors separated by 40 cm?

Infinite number of images will be formed due to multiple reflections of light. The number of images can be determined as;

Q 15:

Two mirrors meet at right angles. A ray of light is incident on one at an angle of 30° as shown in Fig. 16.19. Draw the reflected ray from the second mirror.

The first law of reflection is used to obtain the ray of reflected light.

Here, we can see that the given ray of light will reflect from the second mirror at an angle of 60 degree.

Q 16:

Boojho stands at A just on the side of a plane mirror as shown in Fig. 16.20. Can he see himself in the mirror? Also can he see the image of objects situated at P, Q and R?

Boojho cannot see his image as he is not standing in front of the mirror. He can see the objects situated at P and Q as the light from these two points get reflected by the mirror and reaches his eyes. He cannot see the object at R.

Q 17:

(a) Find out the position of the image of an object situated at A in the plane mirror (Fig. 16.21).
(b) Can Paheli at B see this image?
(c) Can Boojho at C see this image?
(d) When Paheli moves from B to C, where does the image of A move?

This image of the object place at the A, will be formed behind the mirror and it will be at the same distance from the mirror as the object A is placed or present.
Yes, Paheli at B can see the image as the light from B gets reflected by the mirror and reaches A.
Yes, Boojho at C point can see the image as the light from C gets reflected by the mirror and reaches A.
The image A will be stationary even if Paheli moves from B to C.

Q 2:

Differentiate between regular and diffused reflection. Does diffused reflection mean the failure of the laws of reflection?

Difference between the regular reflection and the diffused reflection are as follows:

Regular Reflection	Diffused Reflection
When all the parallel rays reflected from a plane surface are parallel, the reflection is known as regular reflection.	When all the parallel rays reflected from the surface are not parallel, the reflection is known as diffused reflection.
The image formed by the regular reflection is sharp and clear.	The image formed by the irregular reflection is either faint or blurred.
Regular reflection takes place on a smooth surface.	Irregular reflection takes place on the round surface.

No, diffused reflection does not mean the failure of laws of reflection. The laws of reflection are also followed in diffused reflection.

Q 3:

Mention against each of the following whether regular or diffused reflection will take place when a beam of light strikes. Justify your answer in each case.
(a) Polished wooden table (b) Chalk powder
(c) Cardboard surface (d) Marble floor with water spread over it
(e) Mirror (f) Piece of paper

Polished wooden table: Regular reflection will take place because rays of light reflected from the polished wooden table (smooth surface) are parallel.
Chalk powder: Diffused reflection will take place because rays of light reflected from the chalk powder are not parallel due to its round surface.
Cardboard surface: Diffused reflection will take place because rays of light reflected from the cardboard surface; are not parallel due to its rough surface.
Marble floor with water spread over it: Regular reflection will take place because rays of reflect light reflected from the marble surface/ floor spreads on it. Smooth surface are parallel.
Mirror: Regular reflection will take place because rays reflected from the mirror are parallel.
Piece of paper: Diffused reflection will take place because rays of reflection from the piece of paper will not parallel due to its rough surface.

Q 4:

State the laws of reflection.

There are two laws if reflection:

The angle of incidence (∠i) is always equal to the angle of reflection (∠r).
The incident ray, the normal at the point of incidence and the reflected ray, all lie in the same point.

Q 5:

Describe an activity to show that the incident ray, the reflected ray and the normal at the point of incidence lie in the same plane.

The laws of reflection of light can be verified by the following activity:

Pin a white sheet of plane (mirror) paper on a cardboard.
Place a strip of plane mirror M^’on the plane paper.
Pined a 2 pins P₁ and P₂. Obliquely in front of the plane mirror in a straight line so that the line joining the pins can make an angle of 30◦, 45◦ and 60◦ with the normal drawn at the point of incidence.
See through the mirror from other side and observe the pins P₁ and P₂ seen on the mirror and pins P₃ and P₄ appears in the straight line.
Remove the plane mirror and the pins. Encircle the points where pins were fixed on the paper.
Join the P₁ and P₂ extended the line to meet at point O of the mirror. The ray AO so obtained is an incident ray.
Similarly join P₃ and P₄ and extend the line to meet at point O of the mirror. The ray O so obtained is a reflected ray.
Draw a normal OC.
Measure the angle of incidence ∠I and the angle of reflection ∠r. We find that ∠i = ∠r

Conclusion: This activity shows that the mirror incident ray, the reflection ray and the normal at the point of incidence, all lie on the same plane. The angle of the incidence is also equal to the angle of reflection. Thus, this activity verifies the laws of reflection.

Q 6:

Fill in the blanks in the following :
(a) A person 1 m in front of a plane mirror seems to be _______________ m from his image.
(b) If you touch your ____________ ear with right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with ____________
(c) The size of the pupil becomes ____________ when you see in dim light.
(d) Night birds have ____________ cones than rods in their eyes..

(a) 2m

Plane mirror formed images eject as of the image. The distance between the object and image are same here. So, the images 1 + 1 = 2 m. away from the person.

(b) Left, left hand

This is due to the lateral inversion of images which is formed by the plane mirror.

The amount of light entering in the eyes is very little in dim light. Pupil expands to increase the light.

(d) Less

Night birds cannot see in day time because they have large number of rod cells and a few cone cells on their retina.

Q 7:

Angle of incidence is equal to the angle of reflection
(a) Always (b) Sometimes
(c) Under special conditions (d) Never

(a) Always

According to the first law of reflection, the angle of the incidence is always equal to the angle of reflection (∠i = ∠r).

Q 8:

Image formed by a plane mirror is
(a) virtual, behind the mirror and enlarged
(b) virtual, behind the mirror and of the same size as the object
(c) real at the surface of the mirror and enlarged
(d) real, behind the mirror and of the same size as the object.

(b) Virtual, behind the mirror and of the same size as the object

Plane mirror formed the image eject as the size of the object behind the mirror. Images formed by the plane mirror are virtual that is why they cannot be obtained on the screen.

Q 9:

Describe the construction of a kaleidoscope.

A simple device is used to obtain the colorful designs by multiple reflections is called kaleidoscope.

Principle: It works on the principle of multiple reflection of light.

Construction:

Get three rectangular plane mirror strips, each about 15 cm long and 4 cm wide.
Join them together to form a prism.
Pin them in a cylindrical cardboard tube, and make sure that the tube is slightly longer than the mirror strips.
Close the one end of the tube by a cardboard disc having a hole in its center through which you can see.
At the other end, touching the mirrors fix circular glass plate.
Place several small pieces of the coloured glass on this glass plate.
Close (disc) this end of the tube by ground glass plate. Allow enough space for the coloured pieces to move around. This is kaleidoscope.

When seen through the hole, we will be able to see a variety of patterns in the tube.

Frequently Asked Questions about Light - Class 8 Science

- 1. How many questions are covered in Light solutions?
- All questions from Light are covered with detailed step-by-step solutions including exercise questions, additional questions, and examples.
- 2. Are the solutions for Light helpful for exam preparation?
- Yes, the solutions provide comprehensive explanations that help students understand concepts clearly and prepare effectively for both board and competitive exams.
- 3. Can I find solutions to all exercises in Light?
- Yes, we provide solutions to all exercises, examples, and additional questions from Light with detailed explanations.
- 4. How do these solutions help in understanding Light concepts?
- Our solutions break down complex problems into simple steps, provide clear explanations, and include relevant examples to help students grasp the concepts easily.
- 5. Are there any tips for studying Light effectively?
- Yes, practice regularly, understand the concepts before memorizing, solve additional problems, and refer to our step-by-step solutions for better understanding.

Exam Preparation Tips for Light

The Light is an important chapter of 8 Science. This chapter’s important topics like Light are often featured in board exams. Practicing the question answers from this chapter will help you rank high in your board exams.

Latest Blog Posts

Stay updated with our latest educational content and study tips

Smart Questions to Ask in a Parent-Teacher Meeting | PTM Made Easy

Parent-Teacher Meetings (PTMs) are more than quick updates on marks — they’re a chance to build a real partnership between home and school. A good Parent-Teacher Meeting conversation helps parents see beyond grades. It opens up insights about a child’s strengths, struggles, emotions and even hidden talents. When parents participate actively, they don’t just track […]

The Secret to Smarter Learning — Building Strong Critical Thinking Skills

In today’s world of endless information , knowing how to think is more important than knowing what to think . From school projects to real – life decisions , critical thinking helps students question ideas , analyze facts and form logical conclusions . But what exactly does critical thinking mean ? Simply put , it’s […]

Study Smarter, Not Harder: Build Productive Habits That Stick

Every student dreams of better grades , stronger focus and more study time – but the real challenge isn’t starting, it’s staying consistent . Building productive study habits is not about studying all day , it’s about studying smart . In today’s fast – paced digital world, distractions are everywhere – from endless phone notifications […]

The Hidden Risks of Online Gaming for Children — Is your child safe while gaming online?

Online gaming has rapidly become one of the most popular pastimes among children. Whether it’s multiplayer mobile games , PC adventures or console challenges , kids are spending more time than ever in the virtual world . On the surface, gaming seems entertaining and even educational – improving hand- eye coordination , teamwork and problem […]

View All Blog Posts

Benefits of Using Our NCERT Solutions for Class

When it comes to excelling in your studies, having a well-structured study guide can make a huge difference. Our NCERT Solutions for Class provide you with a comprehensive, easy-to-understand, and exam-focused resource that is specifically tailored to help you maximize your potential. Here are some of the key benefits of using our NCERT solutions for effective learning and high scores:

NCERT Solutions for Effective Exam Preparation

Preparing for exams requires more than just reading through textbooks. It demands a structured approach to understanding concepts, solving problems, and revising thoroughly. Here’s how our NCERT solutions can enhance your exam preparation:

Clear Understanding of Concepts: Our NCERT solutions are designed to break down complex topics into simple, understandable language, making it easier for students to grasp essential concepts in . This helps in building a solid foundation for each chapter, which is crucial for scoring high marks.
Step-by-Step Solutions: Each solution is presented in a detailed, step-by-step manner. This approach not only helps you understand how to reach the answer but also equips you with the right techniques to tackle similar questions in exams.
Access to Important Questions: We provide a curated list of important questions and commonly asked questions in exams. By practicing these questions, you can familiarize yourself with the types of problems that are likely to appear in the exams and gain confidence in answering them.
Quick Revision Tool: Our NCERT solutions serve as an excellent tool for last-minute revision. The solutions cover all key points, definitions, and explanations, ensuring that you have everything you need to quickly review before exams.

Importance of Structured Answers for Scoring Higher Marks

In exams, it's not just about getting the right answer—it's also about presenting it in a well-structured and logical way. Our NCERT solutions for Class are designed to guide you on how to write answers that are organized and effective for scoring high marks.

Precise and Concise Answers: Our solutions are crafted to provide answers that are to the point, without unnecessary elaboration. This ensures that you don't waste time during exams and focus on delivering accurate answers that examiners appreciate.
Step-Wise Marks Distribution: We understand that exams often allot marks based on specific steps or points. Our NCERT solutions break down each answer into structured steps to ensure you cover all essential points required for full marks.
Improved Presentation Skills: By following the format of our NCERT solutions, you learn how to present your answers in a systematic and logical manner. This helps in making your answers easy to read and allows the examiner to quickly identify key points, resulting in better scores.
Alignment with NCERT Guidelines: Since exams are often set in alignment with NCERT guidelines, our solutions are tailored to follow the exact format and language that is expected in exams. This can improve your chances of scoring higher by meeting the examiner's expectations.