NCTB Class 6 Science Chapter 9 Phenomenon of Light Solution
Bangladesh Board Class 6 Science Solution Chapter 9 Phenomenon of Light Solution Exercises Question and Answer by Experienced Teacher.
NCTB Solution Class 6 Chapter 9 Phenomenon of Light:
|Board||NCTB Bangladesh Board|
|Chapter Name||Phenomenon of Light|
Fill in the blanks:-
(1) In the plane mirror the angle of incidence and the angle of reflection is——.
(2) If a person stands at a distance of 1 meter from a plane mirror, this image is—– meter.
(3) If you touch your right ear standing in front of a Plane mirror, its image will touch ——.
Ans:- its left ear.
(4) The periscope is made by applying the reflection of light——-.
Multiple choice questions:-
(1) When light falling on an object does not return back, we call it—
Ans:- (a) absorption.
(2) We can see o an object when—-
Ans:- (b) it reflects light.
(3) The volume of <BON in the figure is —-
Ans:- (b) 400
(4) If the incident ray falls along the line PO the value of the angle of reflection will be——
Ans:- (c) 500
Short answer questions:-
(1) Suppose you are in a dark-room. Will you be able to see the things inside the room around you? Will you be able to see the things those are outside the room? Explain, why/why not.
Ans:-If i am in a darkroom the i will not able to see the things inside the room around me. Because there is no light, which reflects or returns form an object to my eyes in the darkroom.
(2)What is the difference between regular and diffused (irregular) reflections?
Ans:-The difference between regular and diffused (irregular) reflection:-
|Regular reflection||Diffused reflection|
|(a) The angle of incident ray and the angle of reflection are equal.
(b) It occurs from smooth or polished surfaces.
|(a) The angle of incident ray and the angle of reflection is different.
(b) It occurs from rough surfaces.
(3) Describe the construction of a periscope.
Ans:- Periscope is made by placing two strips of plane mirrors at the two ends of a long narrow tube. Two mirrors are fitted with the wall of the tube at an angle of 450. They are placed parallel to each other facing sides that diverts the parallel lights falling on them at an angle of 900.
(4) Which of the following substance cause regular reflection and irregular reflection?
Regular reflection is caused by——
(a) Floor of marble, (b) Plane mirror
(c) Polished box, (b) New steel plate
(5) Look at the diagram below and find out the value of the angle.
Ans:-In the diagram there is a plane or smooth surface on which the light falls at an angle of 450. And we know i.e. smooth surface causes, regular reflection where the angle of incident ray= the angle of reflection. So in the following diagram the angle of reflection is also 450.
(1) Shamin got a periscope in his school practical class and looked outside through it. He could see the flowers of the garden outside the class. After the class, he went to the plane mirror fixed above the basin to wash hands. He observed that the closer he approached to the mirror, the closer his image behind the mirror was approaching towards him. Again, when he was going away from the mirror, his image behind the mirror was also going further. On his return home, he designed one periscope placing the mirrors at an angle of 300 using all the required accessories.
(a) What is called reflection of light?
(b) What is image?
(c) Explain the cause of changing of Shamin’s in the mirror?
(d) Will it be possible to see the sceneries outside as in the school by the periscope designed by Shamin at home? Give reasons in favour your answer.
(1) (a) When light falls on an object, if it is obstructed and returns back, it is called reflection of light.
(b) If the light reflected from the object falls on a smooth or glittering surface, an image of the object is formed on that surface.
(c) The cause of changing the position of Shamin’s image in the mirror is Shamin was changed his position from the mirror and image from the plane mirror is equal to the distance of you from the mirror.
(d) It will not possible to see the sceneries outside as in the school by the periscope designed by shamin at home because he designed the periscope placing the mirror at 300angle. But according to the mirror at 450angle.
(2) Two mirror are combined at right angle. A light ray is falling at first mirror making an angle of 20 with it.
(a) What is called reflection?
(b) Write down the principle of reflection.
(c) Draw the reflecting ray from the second mirror.
(d) If the two mirror are kept parallel to each other, what type of reflection will occur and explain why it will occur.
Ans:- (a) When light falls plane or smooth then it is obstructed and returns back from the surface, it called reflection.
(b) The principles of reflection:-
(1)If the surface is plane or smooth then the angle of incident ray and the angle of reflection are equal.
(2) If the surface is rough then the angle of incident ray and the angle of reflection are different.