science - light

Class 8 - Science

Light

Q&A
Notes
Question:

Explain how you can take care of your eyes.

Answer:

To protect our eyes, the given points should be taken into account:
(i)Visit an eye specialist regularly.
(ii)Avoid reading in dim light and very bright light.
(iii)Avoid direct exposure of sunlight to the eye.
(iv)Clean your eyes with cold water quickly if dust particles or small insects enter your eye. Do not rub your eyes.
(v) Maintain a distance of at least 25 cm between the book and your eyes while reading.



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Questions and Answers


Light - Questions
1. State the laws of reflection.
Answer
2. (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?
Answer
3. What is the angle of incidence of a ray if the reflected ray is at an angle of 90° to the incident ray?
Answer
4. 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?
Answer
5. 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 advice?
Answer
6. 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.
Answer
7. Describe the construction of a kaleidoscope.
Answer
8. Differentiate between regular and diffused reflection. Does diffused reflection mean the failure of the laws of reflection?
Answer
9.

Explain how you can take care of your eyes.


Answer
10. 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.
Answer
11. Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room? Explain.
Answer
12. How many images of a candle will be formed if it is placed between two parallel plane mirrors separated by 40 cm?
Answer
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