Reflection of Light Exe-7A Long Answer Concise Physics ICSE Class-9 Selina Publishers

Reflection of Light Exe-7A Long Answer Concise Physics ICSE Class-9 Selina Publishers. There is the solutions of Long Answer type Questions of your latest textbook which is applicable in 2024-25 academic session. Visit official Website CISCE for detail information about ICSE Board Class-9.

Reflection of Light Exe-7A Long Answer Type

Concise Physics ICSE Class-9 Selina Publishers.

Board	ICSE
Class	9
Subject	Physics
Writer / Publication	Concise Selina Publishers
Chapter-7	Reflection of Light
Exe-7A	Laws of Reflection
Topics	Solution of Questions
Academic Session	2024-2025

Exercise- 7A Laws of Reflection

page -170

Long Answer :

Q1- With the help of diagrams, explain the difference between the regular and irregular reflection.

Ans-

Regular reflection occurs when a beam of light falls on a smooth and polished surface and irregular reflection occurs when a beam of light falls on a rough surface. Since the surface is uneven, from different points light rays get reflected in different directions and give rise to irregular reflection.

Q2- State the laws of reflection and describe an experiment to verify them .

Ans- Laws of reflection :-

1. The angle of incidence is equal to the angle of reflection.
2. The incident ray, the reflected ray and the normal at the point of incidence, lie in the same plane.

Experiment to verify the laws of reflection:

Fix a white sheet of paper on a drawing board and draw a line MM₁ as shown in figure. On this line, take a point O nearly at the middle of it and draw a line OA such that ∠MOA is less than 90^o. Then draw a normal ON on line MM₁ at the point O, and place a small plane mirror vertical by means of a stand with its silvered surface along MM₁.

Next fix two pins P and Q at some distance (≈5 cm) apart vertically on line OA, on the board. Keeping eye on the other side of normal (but on the same side of mirror), see clearly images P’ and Q’ of the pins P and Q. Next fix a pin R such that it is in line with the images of pins P and Q as observed in the mirror. Next, fix one more pin S such that the pin S is in line with the pin R as well as images P’ and Q’ of pins P and Q.

Draw small circles on paper around the positions of pins as shown in figure. Remove the pins and draw a line OB joining the pin points S and R, which meets the surface of mirror at O. The angles AON and BON are measured and recorded.

 repeat experiment

The experiment is then repeated for the angle of incidence ∠AON equal to 40^o, 50^o, 60^o.
From results, it is observed that angle of incidence is equal to the angle of reflection. This verifies the first law of reflection.

The experiment has been performed on a flat drawing board, with mirror normal to the plane of board on which white sheet of paper is being fixed. Since the lower tips of all the pins also lie on the same plane (i.e., the plane of paper), it proves the second law of reflection.

Q3- Figure shows an incident ray AO and the normal ON on a plane mirror. The angle which the incident ray AO makes with mirror is 30°. (a) Find the angle of incidence. (b) Draw the reflected ray and then find the angle between the incident and reflected rays.

Ans- (a) Angle of incidence = 90^o – 30^o = 60^o

(b) Angle between the incident ray and reflected ray = Angle of incidence + Angle of reflection

Angle of reflection = Angle of incidence = 60^o

Therefore, Angle between the incident ray and reflected ray = 60^o + 60^o = 120^o

Q4- The diagram in Figure shows a point object P in front of a plane mirror MM₁.

(a) Complete the diagram by taking two rays from the point P to show the formation of its image.

(b) In the diagram, mark the position of eye to see the image.

(c) Is the image formed real or virtual? Explain why?

Ans (a) and (b)

(c) The image formed is virtual because the reflected rays meet when produced backwards.

Q5- The diagram below in figure shows an object XY in front of a plane mirror MM₁ . Draw on the diagram, path of two rays from each point X and Y of the object to show the formation of its image .

Ans-

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