Uses of Spherical Lens

Q.

State any two uses of convex lenses.

Q.

What is a magnifying glass ? State its two uses.

Q.

Draw a diagram to show how a converging lens held close to the eye acts as a magnifying glass. Why is it usual to choose a lens of short focal length for this purpose rather than one of long focal length ?

Q.

State two applications each of a convex and concave lens.

Q. Mention the kind of lens that can form Real and inverted and magnified image

Q. The lens of the goggles are curved but why doesn't it has power?

Q.

The objective lens of microscope use

1. Convex mirror

2. Concave lens

3. Concave mirror

4. Convex lens

Q.

A magnifying glass forms :

(a) a real and diminished image

(b) a real and magnified image

(c) a virtual and magnified image

(d) a virtual and diminished image.

Q.

Draw a ray diagram to show how a converging lens can form an image of the sum. Hence give a reason for the term 'burning glass' for a converging lens used in this manner.

Q. A 2 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 10 cm. The distance of object from the lens is 15 cm. Find the position, nature and size of the image. Calculate the magnification of the lens.
[4 Marks]

Q.

The diagram given below shows an object $ \mathrm{O}$ and its image $ \mathrm{I}$. Without actually drawing the ray diagram, state the type of lens (Converging / Diverging).

Q.

The smaller the focus of a convex lens, more its magnifying capacity, so why don't we use magnifying glasses with very small focal length?

1. They would be too heavy.

2. They are difficult to manufacture.

3. One would have to hold the magnifying glass to close to the object.

4. The image will be too big for our liking.

Q.

How mirrors are used in early days

Q.

Question 37
Define power of a lens. What is its unit? One student uses a lens of focal length 50 cm and another of –50 cm. What is the nature of the lens and its power used by each of them?

Q. This section contains 1 Matrix Match type question, which has 2 Columns (Column I and Column II). Column I has four entries (A), (B), (C) and (D), Column II has four entries (P), (Q), (R) and (S). Match the entries in Column I with the entries in Column II. Each entry in Column I may match with one or more entries in Column II.
इस खण्ड में 1 मैट्रिक्स मिलान प्रकार का प्रश्न है, जिसमें 2 कॉलम (कॉलम I तथा कॉलम II) हैं। कॉलम I में चार प्रविष्टियाँ (A), (B), (C) तथा (D) हैं, कॉलम II में चार प्रविष्टियाँ (P), (Q), (R) तथा (S) हैं। कॉलम I में दी गयी प्रविष्टियों का मिलान कॉलम II में दी गयी प्रविष्टियों के साथ कीजिए। कॉलम I में दी गयी प्रत्येक प्रविष्टि का मिलान कॉलम II में दी गयी एक या अधिक प्रविष्टियों के साथ हो सकता है।

Match the Columns and choose the appropriate answer

कॉलमों का मिलान करें और सही उत्तर चुनें

	Column-I कॉलम-I		Column-II कॉलम-II
(A)	Concave lens अवतल लेन्स	(P)	Used for rear view in automobiles वाहनों में पश्च दृष्टि के लिए प्रयुक्त होता है
(B)	Concave mirror अवतल दर्पण	(Q)	Used as a reflector in solar cooker सौर कूकर में परावर्तक के रूप में प्रयुक्त होता है
(C)	Convex lens उत्तल लेन्स	(R)	|m| < 1
(D)	Convex mirror उत्तल दर्पण	(S)	|m| > 1

1. A-R, B-QRS, C-RS, D-PR
2. A-P, B-PRS, C-QS, D-PQ
3. A-RS, B-QS, C-QR, D-PQ
4. A-PS, B-RS, C-PQRS, D-QS

Q.

The smaller the focus of a convex lens more will be its magnifying capacity, so why don't we use magnifying glasses with very small focal length?

1. They are difficult to manufacture.

2. The image will be too big for our liking.

3. One would have to hold the magnifying glass to close to the object.

4. They would be too heavy.

Q.

Complete the following table:

1. Virtual and upright; Highly magnified

2. Virtual and upright; Highly diminished

3. Real and inverted; Highly diminished

4. Real and inverted; Highly magnified

Q. Supply the information from the passage.

Q. A person who is near sighted will have the most trouble reading

1. a newspaper in his hands
2. a mobile screen in front of him
3. a street sign across the street
4. the menu in a restaurant

Q. A person is viewing an extended object. If a converging lens is placed in front of his eyes, will he feel that the size has increased?

Q.

Draw a diagram to show how a converging lens held close to the eye acts as a magnifying glass. Why is it usual to choose a lens of short focal length for this purpose rather than one of long focal length ?

Q. This section contains 1 Matrix Match type question, which has 2 Columns (Column I and Column II). Column I has four entries (A), (B), (C) and (D), Column II has four entries (P), (Q), (R) and (S). Match the entries in Column I with the entries in Column II. Each entry in Column I may match with one or more entries in Column II.
इस खण्ड में 1 मैट्रिक्स मिलान प्रकार का प्रश्न है, जिसमें 2 कॉलम (कॉलम I तथा कॉलम II) हैं। कॉलम I में चार प्रविष्टियाँ (A), (B), (C) तथा (D) हैं, कॉलम II में चार प्रविष्टियाँ (P), (Q), (R) तथा (S) हैं। कॉलम I में दी गयी प्रविष्टियों का मिलान कॉलम II में दी गयी प्रविष्टियों के साथ कीजिए। कॉलम I में दी गयी प्रत्येक प्रविष्टि का मिलान कॉलम II में दी गयी एक या अधिक प्रविष्टियों के साथ हो सकता है।

Match the Columns and choose the appropriate answer

कॉलमों का मिलान करें और सही उत्तर चुनें।

	Column-I कॉलम-I		Column-II कॉलम-II
(A)	Radius of curvature in cm is cm में वक्रता त्रिज्या है	(P)	Virtual आभासी
(B)	Focal length of mirror in cm is cm में दर्पण की फोकस दूरी है	(Q)	Diminished छोटा
(C)	Nature of image is प्रतिबिम्ब की प्रकृति है	(R)	40
(D)	Nature of image is प्रतिबिम्ब की प्रकृति है	(S)	10

1. A-S, B-P, C-PR, D-R
2. A-P, B-Q, C-QS, D-S
3. A-R, B-S, C-PQ, D-Q
4. A-Q, B-R, C-RS, D-P

Q.

State two applications each of a convex and concave lens.

Q.

State uses of a convex lens.

Q. A telescope makes use of

1. convex lenses
2. neither convex nor concave lenses
3. concave lenses
4. either convex or concave lenses

Q. Which of the following materials cannot be used to form a lens?

1. Clay
2. Glass
3. Water
4. Plastic

Q. Question 1
Define 1 dioptre of power of a lens.

Q.

What type of lens would you use as a magnifying glass ? How close must the object be to the lens ?

Q.

Complete the following table:

1. Real and inverted; Highly diminished

2. Real and inverted; Highly magnified

3. Virtual and upright; Highly magnified

4. Virtual and upright; Highly diminished

Q. (i) What is magnifying glass? State its two uses.

(ii) Write an expression for the magnifying power of a simple microscope. How can it be increased?