What Do You Understand by Focal Plane of a Lens? - Physics

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Short Note
What do you understand by focal plane of a lens?
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Solution

Focal plane of a lens: Rays of light can pass through the lens in any direction and hence there will be two focal planes on either side of the lens and they are referred to as the first focal plane and the second focal plane of a lens:
(i) First focal plane: It is the plane passing through the first focal point and normal to the principal axis of the lens.
(ii) Second focal plane: It is the plane passing through the second focal point and normal to the principal axis of the lens.

Concept: Lens
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Chapter 2: Light - Exercise 2.2 i [Page 101]

APPEARS IN

Frank ICSE Class 10 Physics Part 2
Chapter 2 Light
Exercise 2.2 i | Q 8 | Page 101

RELATED QUESTIONS

The following  diagram shows the experimental set up for the determination of focal length of a lens using a plane mirror.


(i) draw two rays from the point O of the object to show the formation of image I at O itself.
(ii) What is the size of the image I?
(iii)State two more characteristics of the image I.
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(v) To what point will the rays return if the mirror is moved away from the lens by a distance equal to the focal length of the lens ?


Match the columns in the following table and explain them.

Column 1 Column 2 Column 3
Farsightedness
Nearby object can be seen clearly
Bifocal lens
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Nearsightedness Problem of old age Convex lens

(i) If the lens is placed in water instead of air, how does its focal length change ? 
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What will be the behaviour of a lens, if it is placed in water instead of air?


We can burn a piece of paper by focussing the sun rays by using a particular type of lens. Name the type of lens used for the above purpose.


A converging lens is used to obtain an image of an object placed in front of it. The inverted image is formed between F2 and 2F2 of the lens. Where is the object placed?


From the nature of the refracted rays, shown in the diagram interpret the nature of the lens represented by the dotted line.


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Write the name.

The imaginary line passing through two optical centres of lens


The virtual image of object seen by the eye depends on the angle subtended by the object with the eye.


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Focal length


Write law in a given figure.


Write law in a given figure.


Explain with a ray diagram the position, size, and nature of the various image formed by convex lenses.

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Explain with a ray diagram the position, size, and nature of the various images formed by the convex lens.

An object beyond 2F1.


Explain with a ray diagram the position, size, and nature of the various images formed by a convex lens.

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The image formed by a lens is always virtual, erect and smaller in size than an object kept at different positions in front of it. Identify the nature of the lens.


State whether the following statement is True or False

A concave lens can be used to produce an enlarged and erect image.


State whether the following statement is True or False

A convex lens always produces a real image.


Observe the figures given in Figure 15.1 carefully.

The given figures show the path of light through lenses of two different types, represented by rectangular boxes A and B. What is the nature of lenses A and B?


Two different types of lenses are placed on a sheet of newspaper. How will you identify them without touching them?


It was observed that when the distance between an object and a lens decreases, the size of the image increases. What is the nature of this lens? If you keep on decreasing the distance between the object and the lens, will you still be able to obtain the image on the screen? Explain.


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A point object is placed at a distance of 60 cm from a convex lens of focal length 30 cm. If a plane mirror were put perpendicular to the principal axis of the lens and at a distance of 40 cm from it, the final image would be formed at a distance of :


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Distinguish between:

Concave Lens and Convex Lens


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