DAV class 7 Science Chapter 12 Solutions | Light Question Answer

October 26, 2021 Deepak Kumar DAV Class 7 2

DAV Class 7 science chapter 12 solutions

Light is an important chapter in DAV Class 7 Science textbook.  It talks about the laws of reflection, the types of spherical mirrors and the image formation for them. We have given accurate answers for Class 7 Science Light Question answers with explanation

 

DAV Class 7 Science Chapter 12 Solutions

Let us check out the solutions of DAV Class 7 Light Question Answers, Back exercise solutions.

A. Fill in the blanks.

1. An image, which can be obtained on a screen, is called a ___________ image.

2. The angle of reflection ___________ the angle of incidence.

3. The incident ray, the ___________ at the point of incidence and the reflected ray all lie in the same ___________.

4. The point, where a concave mirror forms the image of a very distant object, is known as the ___________ of the mirror.

5. A spherical mirror, that always forms a virtual, erect and diminished image of an object, is a ___________ mirror.

6. Eye specialists use ophthalmoscope, which is fitted with ___________ mirror.

Answer:

1) Real

2) equals

3) normal

4) Focus

5) Convex

6) Concave

Also Check: DAV Class 7 Science Chapter 5 Solutions

 

B. Write True or False for the following statements.

1. The image, formed by a plane mirror, shows the right side of the object as its right side and the left side of the object as its left side.

2. When we stand between a pair of parallel plane mirrors, we can see an infinite number of images.

3. A concave mirror can never form a virtual image of an object.

4. We can use either a concave mirror, or a convex mirror, as the ‘reflector’ in torches.

5. Motor vehicles generally use either a plane mirror, or a convex mirror, as their ‘rear view’ mirror.

Ans 1. False

2. True

3. False

4. False

5. True

C. Tick the correct option

Refer the questions from your textbook.

(1) normal on the point of incidence.

(2) it just retraces the path.

(3) Pole of the mirror.

(4) 4 m

(5) 8 m/s

Also Read: Transportation in Plants and Animals Question Answers

 

D. Answer the following questions in brief.

1. Explain clearly the difference between a real image and a virtual image. Give one example of a virtual image.

Answer: 

2. How does changing the distance of the object, from a convex mirror, affect the size and nature of the image formed by it?

a) If we move the objects towards a convex mirror, the size of the image will increase.

b) When we move the object away from the mirror, the size will decrease.

c) Nature of the image will remain the same in both the cases.

3. Draw a ray diagram to show the formation of an image when the object is placed between the C and F points of a concave mirror.

 

4. Where should we keep an object, in front of a concave mirror, so as to get a virtual and magnified image of it?

In order to obtain a virtual and magnified image of the object, we should keep an object in front of a concave mirror between focus F and Pole, P of the concave mirror.

5.  The magnified image, of an object, appears to be formed, behind the mirror, by an apparent intersection of the reflected rays. What can you say about (a) nature of the image (b) the type of mirror used?

a) The image formed will be Virtual in nature. (b) A concave mirror has been used.

6. Rohit suggested to his father to fix a ‘security mirror’ which would provide them with a wider view of the surrounding of their shop. Name the type of mirror that Rohit must have suggested to his father. Also mention the basic characteristics of the image formed by this type of mirrors.

Type of mirror his father should use – Convex mirror

Characteristics of the image formed by this mirror are as follows –

  • Image is formed behind the mirror in a convex mirror case.
  • The size of the image increases when we move the object towards the mirror.
  • The image formed by a convex mirror is virtual, erect and diminished in nature.
  • The size of the image will decrease when we move objects far away from the convex mirror.

7. State the type of mirror that the following items/objects would correspond to:

(a) inside of a stainless-steel bowl

(b) reflector of a torch

(c) a polished shining wooden surface

(d) the shiny outer surface of the bicycle bell.

Ans 7:

a) The inside of a stainless comes under the category of Concave Mirror

b) The reflector of a torch comes under the category of Concave Mirror

c) A Polished shining wooden surface will come under the category of a plane mirror.

d) The shiny outer surface of the bicycle bell comes under the Convext mirror.

E. Answer the following questions.

1. State the laws of reflection. Describe an activity to show that incident ray, reflected ray and the normal, at the point of incidence, all lie in same plane.

Ans: 

Laws of Reflection states:

  • 1. The incident ray, the normal at the point of incidence and reflected ray, all lie in the same plane.
  • 2. The angle of incidence, and the angle of reflection, are equal to each other.

Activity

The incident ray, reflected ray and the normal, at the point of incidence, all lie in same plane. Let us understand this concept with the help of an example.

Take a plane mirror. Place the mirror on the table perpendicular to the table. Take a sheet and put it perpendicular to the table. Now take another sheet and draw a normal on the sheet with the help of a pencil and a scale. On the first sheet make a hole such that light can enter through it. Take a torch and allow the torch light to pass through it.

Make sure the light in the room is not too bright. Then allow the torch light fall on the normal point to the mirror. You will observe that the light reflects back and the reflected ray is formed on the same sheet of paper on which the incident ray was formed. This shows that the incident ray, the normal at the point of incidence and the reflected ray all lie in the same plane.

2. Trace the path of reflected ray in the following ray diagrams.

Ans: Try it on your own.

3. Draw a ray diagram to show the formation of the image of a point object by

(i) a plane mirror and (ii) a convex mirror.

Ans 1 Refer to page no. 180 of your science book.

4. Three persons are standing at points P, Q and R in front of a plane mirror. Can ‘P’ see himself in the mirror? Also, can he see the image of Q and R in the mirror?

Answer: No, person P will not be able to see an image of himself in the mirror but yes, he can see an image of persons Q and R in the mirror.

5. With the help of a suitable diagram, explain the meaning of the following terms for a concave mirror.

(a) centre of curvature

(b) pole

(c) principal axis

(d) focus

a) The Centre of curvature is the centre of a sphere whose part is the spherical mirror.

b) Pole of the mirror is a central point lying on the spherical mirror.

c) Principal Axis is an imaginary line that joins the Pole of the mirror and the centre of curvature.

d) Focus of the mirror is such a point that all the lines parallel to the principal axis will meet or appear to meet at the point.

6. What type of mirror is used in the following cases? Is the image formed virtual and erect in each case?

(a) ‘make up’ mirror

(b) ‘rear view’ mirror of vehicles

(c) reflecting type telescope

(d) shaving mirror

a) Plane mirror is used as a makeup mirror

b) The Rearview mirror of vehicles is convex in nature.

c) The reflecting type of telescope is a curved mirror

d) Shaving mirror is concave in nature.

No, we will not get a virtual and erect image in each case. Nature of the image varies in each case given above.

 

 

 

 

 

 

 

 

 

 

 

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