NCERT Class 8 Science Chapter 16 Light

NCERT Class 8 Science Chapter 16 Light Solutions to each chapter is provided in the list so that you can easily browse through different chapters NCERT Class 8 Science Chapter 16 Light and select need one. NCERT Class 8 Science Chapter 16 Light Question Answers Download PDF. NCERT Class 8 Science Solutions.

NCERT Class 8 Science Chapter 16 Light

Join Telegram channel

Follow us:

Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. CBSE Class 8 Science Solutions are part of All Subject Solutions. Here we have given NCERT Class 8 Science Chapter 16 Light and Textbook for All Chapters, You can practice these here.

Light

Chapter: 16

NCERT TEXT BOOK EXERCISES

Q. 1. Suppose you are in a dark room. Can you see objects outside the room? Explain.

Ans. When we are in a dark room then we do not see objects. We can see the objects outside the room because out of the room the light is available and that rays of light enter in our eyes after reflection.

Q. 2. Differentiate between regular and diffused reflection. Does diffused reflection mean the failure of the laws of reflection?

Ans.

Diffused reflection is not due to the failure of the laws of reflection. It is caused by the irregularities in the reflecting surfaces.

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.

Ans. A polished wooden table will have regular reflection because its surface is smooth.

(b) Chalk powder.

Ans. A chalk powder will get the diffused reflection because chalk particles are not smooth. 

(c) Cardboard surface.

Ans. Cardboard surface has minute irregularities on it, so it will have a diffused reflection. 

(d) Marble stone with water spread over it.

Ans. Marble stone with water spread over it will have regular reflection if water is stable but if waves are formed then diffused reflection will take place. 

(e) Mirror.

Ans. A mirror will reflect light regularly due to its smooth surface.

(f) Piece of paper.

Ans. A piece of paper will have irregular reflection due to minute irregularities on it.

Q. 4. State the laws of reflection.

Ans. Following are the laws of reflection: 

(i) Incident ray, reflected ray and normal drawn at the point of incidence to the reflecting surface always lie in the same plane.

(ii) Angle of incidence is always equal to angle of reflection.

Q. 5. Describe an activity to show that the incident ray, the reflected ray and the normal at the point of incident lie in the same plane.

Ans. Take a white sheet, spread it on a table. Draw a line MM’ on it. Place a plane mirror vertically on this line. Now throw light on a comb in this ways that a parallel light rays fall on the mirror. Adjust it in such a way that a beautiful pattern of incident and reflected rays is formed. Now mark points A, B, C on incident ray and points D, E, F on its corresponding reflected ray. Switch off the torch and remove the mirror. Join the points and extend line ABC to meet MM’ at O and DEF will all also be meeting at O. OA is incident ray and OF is reflected ray. Draw ON ⊥ MM’. This shows that incident ray, reflected ray and normal, all lie in one plane.

Q. 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.

Ans. 2 m.

(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 __________.

Ans. left, left.

(c) The size of the pupil becomes _________ when you see in dim light.

Ans. increase.

(d) Night birds have __________ cones than rods in their eyes.

Ans. lesser.

Choose the correct option in the Questions 7-8. 

Q. 7. Angle of incidence is equal to the angle of reflection:

(i) Always.

(ii) Sometimes.

(iii) Under special conditions.

(iv) Never.

Ans. (i) Always.

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.

Ans. (b) virtual, behind the mirror and of the same size as the object. 

Q. 9. Describe the construction of the human eye.

Ans. The kaleidoscope consists of three long and narrow strips of plane mirrors inclined at 60° to one another forming a hollow prism and fitted into a cardboard tube. One end of the cardboard tube is closed by an opaque disc (cardboard disc) having a small hole at its center. The other end of cardboard tube is closed with two circular discs of glass: the inner disc being of transparent glass and the other disc of ground glass. A number of small pieces of different coloured glass (or plastic) and having different shapes are kept between the two glass discs.

Q. 10. Draw a labeled sketch of the human eye.

Ans. Labeled diagram to show different parts of 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 teacher’s advise?

Ans. Teacher has advised her to because laser light is harmful for eyes and can cause some permanent damage to eyes when throw directly in eyes.

Q. 12. Explain how you can take care of your eyes?

Ans. Following precautionary measures can be taken to take care of our eyes:

(i) We should atleast always wash our eyes with plane cold water atleast three times a day

(ii) We should not touch our eyes with dirty hands.

(iii) We should never rub our eyes.

(iv) We should not look at Sun directly.

(v) We should read book, watch T.V., read from black board from a suitable distance.

(vi) Consult an eye specialist if have any irritation, redness in the eyes.

Q. 13. What is the angle of incidence of a ray if the incident and reflected rays is at an angle of 90° to the incident ray?

Ans. The angle of incidence of the ray will be 45°.

Q. 14. How many images of a candle will be formed if it is placed between two parallel plane mirrors separated by 40 cm?

Ans. Infinite images will be formed.

Q. 15. Two mirrors meet at right angles. A ray of light is incident on one at an angle of 30° as shown in the figure. Draw the reflected ray from the second mirror.

Ans.

Q. 16. Bhoojo 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 image of objects situated at P, Q and R?

Ans. Bhoojo can’t see his image himself. He can see the images of objects at P but not Q and R.

Q. 17. (a) Find out the position of the image of an object situated at A in the plane mirror, (figure)

(b) Can Paheli at B see this image?

(c) Can Bhoojo at C see this image?

(d) When Paheli moves from B to C where does not the image of A move?

Ans. (b) Yes, Paheli can see the image at B.

(c) Yes, Bhoojo can see the image.

(d) No change of image A.