Latest Updated : October 2023
Table of Contents
NCERT Solutions for Class 8 Science Chapter 13 Light will assist you in scoring more marks. This includes the textbook and their solutions for Light Chapter 13 of Class 8 Science, which is made in adherence to the updated syllabus 2023 released by CBSE.
Our solutions offer ample material to help students build a strong foundation and improve their understanding of the subject.
On this page, you will find all the NCERT Solutions for Class 8 Science Chapter 13 Light which includes detailed exercise-based solutions. These NCERT Solutions for Class 8 Science are downloadable and easy to access. Our Science experts have meticulously developed these NCERT Solutions for Class 8 to support students in preparing for their Class 8 exams.
NCERT Solutions for Class 8 Science Chapter 13 Light
Light Class 8 Science NCERT Textbook Questions
Exercise Questions
1. Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room. Explain.
Solution:
When we are in a dark room, we cannot see any objects. This is because only those objects from which reflected rays enter our eyes but in a dark room no light is reflected by the objects. We can see objects outside the room because out of the room the light is available and those rays of light enter our eyes after reflection.
2. Differentiate between regular and diffused reflection. Does diffused reflection mean the failure of the laws of reflection?
Solution:
| Regular Reflection | Diffused Reflection |
| (i) It takes place on a smooth surface. | (i) It takes place on a rough surface. |
| (ii) Reflected rays move in a particular direction. | (ii) Reflected rays are scattered in random directions. |
| (iii) All the reflected rays are parallel. | (iii) All the reflected rays are not parallel. |
| (iv) Example – Reflection by plane mirror. | (iv) Example- Reflection by road surface. |
No, diffuse reflection doesn’t mean the failure of laws of reflection. It is caused by the irregularities in the reflecting surface.
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
Solution:
(a) Polished wooden table- A polished wooden table will have a smooth surface, therefore regular reflection will take place.
(b) Chalk powder- Chalk powder when spread, will have irregularities and a rough surface therefore diffused reflection will take place.
(c) Cardboard surface- Cardboard surface is irregular in nature, so diffused reflection will take place.
(d) Marble floor with water spread over it – It will have a smooth surface, therefore regular reflection will take place.
(e) Mirror- Mirror has smooth surface, therefore regular reflection will take place.
(f) Piece of paper- A piece of paper may look smooth but it has many irregularities on its surface. Therefore, it will give a diffused reflection.
4. State the laws of reflection.
Solution:
The laws of reflection are-
(i) The angle of incidence is always equal to the angle of reflection.
(ii) The incident ray, the normal and the reflected ray, all lie in the same plane.
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.
Solution:
Activity – To show that the incident ray, the reflected ray and the normal at the point of incidence lie in the same plane.
Materials required- Plane mirror, paper, table, torch.
Procedure- Place a plane mirror vertically on a table in a dark room. Create a small hole in a piece of paper and hold it vertically above the table. Take another sheet of paper and lay it flat on the table, ensuring it touches the mirror. Draw a line perpendicular to the mirror on the paper that’s on the table. Now, shine a light beam through the small hole so that it strikes the mirror’s surface perpendicularly. If the light beam meets the mirror, it will be reflected. By observing the paper on the table, it becomes evident that the incoming light ray, the normal line, and the reflected ray at the point of contact all exist within the same plane.
6. Fill in the blanks in the following.
(a) A person 1 m in front of a plane mirror seems to be ______________ m away 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.
Solution:
(a) A person 1 m in front of a plane mirror seems to be 2 m away from his image.
(b) If you touch your left ear with right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with left hand.
(c) The size of the pupil becomes large when you see in dim light.
(d) Night birds have lesser cones than rods in their eyes.
7. Angle of incidence is equal to the angle of reflection.
(a) Always
(b) Sometimes
(c) Under special conditions
(d) Never
Solution: (a) Always
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.
Solution: (b) virtual, behind the mirror and of the same size as the object.
9. Describe the construction of a kaleidoscope.
Solution:
Kaleidoscope is a device based on the principle of multiple reflections. Kaleidoscope is made up of three rectangular mirror strips each about 15 cm long and 4 cm wide. Join them together to form a prism. Fix them in circular cardboard tube. Make sure that the tube is slightly longer than the mirror strips. Close one end of the tube by a cardboard disc having a hole in the centre. To make the disc durable, paste a piece of transparent plastic sheet under the cardboard disc. At the other end, touching the mirrors, fix a circular plane glass plate.
10. Draw a labelled sketch of the human eye.
Solution:
11. Gurmit wanted to perform Activity 13.8 using a laser torch. Her teacher advised her not to do so. Can you explain the basis of the teacher’s advise?
Solution:
Laser light is very harmful for her eyes and can cause a permanent defect in the eye. Person can even lose his or her eyesight if laser torch is directed over the eyes. Therefore, teacher advised Gurmit not to do so.
12. Explain how you can take care of your eyes.
Solution:
We can take care of our eyes in the following ways-
(i) Washing our eyes with clean water frequently.
(ii) Not rubbing our eyes with dirty hands.
(iii) Reading in proper light. Lighting should not be very dim or very bright
(iv) Keeping an average distance of 25cm while reading a book.
(v) Visiting an eye specialist in frequent interval of time.
13. What is the angle of incidence of a ray if the reflected ray is at an angle of 90° to the incident ray?
Solution:
According to the laws of reflection that angle of incidence is equal to angle of reflection.
Here, the angle between the incident ray and reflected ray is 90°
i.e ∠i + ∠r = 90°
∠i = ∠r ( acc to law of reflection)
Therefore we can write ,
∠i + ∠i = 90°
⇒ 2∠i = 90°
⇒ ∠i = 45°
Angle of incidence = 45°
14. How many images of a candle will be formed if it is placed between two parallel plane mirrors separated by 40 cm?
Solution: Infinite number of images.
15. Two mirrors meet at right angles. A ray of light is incident on one at an angle of 30° as shown in Figure. Draw the reflected ray from the second mirror.
Solution:
16. Boojho stands at A just on the side of a plane mirror as shown in Figure. Can he see himself in the mirror? Also can he see the image of objects situated at P, Q and R?
Solution:
Boojho cannot see his image because the reflected ray won’t reach his eyes. He can see the image of objects situated at P and Q because the rays coming from P and Q get reflected by the mirror and reach his eyes. Boojho can’t see the image of objects situated at R because the ray from object R does not get reflected.
17. (a) Find out the position of the image of an object situated at A in the plane mirror as shown in the figure.
(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?
Solution:
(a) The image of the object at position A will be formed behind the mirror and the distance of the image will be same as the distance of the object from the mirror.
(b) Yes, Paheli at B see this image because reflected ray from A will reach B.
(c) Yes, Boojho at C see the image of A.
(d) Image of A will not move as the object is not moving.
Summary
On our platform ncertforclass8.com, you will get all the solutions expertly solved, ensuring utmost care and accuracy. The NCERT book for Class 8 Science is strictly followed while creating these solutions, adhering to the latest CBSE guidelines for NCERT Class 8 Science. We make sure to provide you quality content which will help you to understand the concepts in the best way possible. Also our solutions are completely free for you to access. You have the freedom to copy the NCERT Solutions for Class 8 Science, download them and even create PDF’s, making it convenient for your offline use.
If you are looking for free NCERT Solutions for Class 8 Science, you can bookmark our site ncertforclass8.com and you can download the free PDFs and also share them with your friends. We are currently working to provide you with the best solutions with the updated syllabus, so in case some things aren’t available at this point in time, they will be available soon. Also, feel free to reach out and ask your doubts or queries in the comments below. Happy Learning!
More CBSE Class 8 Study Materials-
- NCERT Solutions for Class 8 English
- NCERT Solutions for Class 8 Maths
- NCERT Solutions for Class 8 Social Science
- NCERT Solutions for Class 8 Science
- NCERT Solutions for Class 8 Sanskrit
- NCERT Solutions for Class 8 Hindi
- NCERT Solutions for Class 8 English Honeydew
- NCERT Solutions for Class 8 English It So Happened
- NCERT Solutions for Class 8 Hindi Bharat Ki Khoj
- NCERT Solutions for Class 8 Hindi Vasant Bhag 3
- NCERT Solutions for Class 8 Science
- NCERT Solutions for Class 8