NCERT Solutions For Class 8 Science Chapter 13 Light SAQs

NCERT Solutions For Class 8 Science Chapter 13 Light SAQs

Question 1. Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room? Explain.
Answer: In the dark room, we cannot sec objects because the objects are visible only when light from an object enters in our eyes. We can see the objects outside the room, if there is light outside. If there is no light outside the room again, we cannot see the object.

Question 2. Differentiate between regular and diffuse reflection. Does diffused reflection mean the failure of the laws of reflection?
Answer: Differences between regular and diffuse reflection are

No, the diffused reflection does not mean the failure of the laws of reflection.

NCERT Class 8 Science Chapter 13 Light Solutions

Question 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.

1) Polished wooden table

Answer: Polished wooden table As the surface is smooth, so there is a regular reflection through it.

2) Chalk powder

Answer: Chalk powder Since, the surface is not smooth or it is uneven, thus there is a diffused reflection through it.

3) Cardboard surface

Answer: Cardboard surface As its surface is uneven, so it will produce a diffused reflection.

4) Marble floor with water spread over it

Answer: Marble floor with water spread over it As marble floor itselfis very smooth, besides this there is a layer of water on it which makes the surface regular for reflection.

NCERT Solutions for Class 8 Science Chapter 13 Light

5) Mirror

Answer: Mirror Since, the surface of mirror is smooth, thus it will produce a regular refelection.

6) Piece of paper
Answer: Piece of paper Since, the surface is uneven, thus It will produce a diffused reflection.

Question 4. State the laws of reflection.
Answer: There are two laws of reflection as below

1. The angle of incidence is equal to the angle of reflection.
2. Incident ray, reflected ray and the normal drawn at the point of incidence to the reflecting surface, all lie in the same plane.

Question 8. Gurmlt wnntod to porform nn activity uxlntf a lavrr torch. Horo, toochor advised her not to do so. Can you explain tho basis of tho tonchor’s advise?
Answer: Laser light comes from a very small hole and the lern of the laser light Is also very small, so the light will penetrate into one part of the eye and it can Injure the retina, whereas the normal torch spreads out the light which does not cause any harm to our eyes. So, the beam of laser light should not be used to perform an activity.

Question 9. Explain how you can take care of your eyes?
Answer: We can take care of our eyes in the following manner

1. If advised, use suitable spectacles.
2. Too little or too much light is bad for eyes. Insufficient light can cause eye strain and headache.
3. Too much light like that of the sun, a powerful lamp or a laser torch can injure the retina.
4. Wash the eyes frequently with clean water.
5. Always read at normal distance for vision.
6. Never rub your eyes.

NCERT Solutions for Light Chapter 13 Class 8

Question 10. What is the angle of incidence of a ray, if the reflected ray is at an angle of 90° to the incident ray?

Answer: We know that, the angle of incidence is equal to the angle of reflection and the reflected ray is at an angle of 90° to the incident ray.

Zi=Zr = 45°

Question 11. How many images of a candle will be formed, if it is placed between two parallel plane mirrors separated by 40 cm?

Answer: Infinite number of images will be formed due to multiple reflections of light.

Question 12. Two mirrors moot 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.

Answer: The diagram will be as follows