Types of spherical lenses

Q.

Choose the correct option.

1. convex mirror has negative focal lengths concave lens have positive focal length

2. convex mirror has positive focal length and concave lens have positive focal length

3. convex mirror has positive focal length and concave lens have negative focal length

4. both convex mirror and convex lens have negative focal length.

Q.

An air bubble inside water behaves like a _________ lens.

Q.

Draw ray diagrams to represent the nature, position and relative size of the image formed by a convex lens for the object placed : (a) at $2F_1$, (b) between $F_1$ and the optical centre O of the lens. Which of the above two cases shows the use of the convex lens as a magnifying glass ? Give reasons for your choice.

Q.

The principal focus of a concave mirror is real while that of a convex mirror is.......................

Q.

A magnifying glass forms

1. Inverted Image

2. Real Image

3. Virtual Image

4. Both A and B

Q. a) Which type of lens is used in a magnifying glass?
b) By drawing a ray diagram, explain the formation of an image by a simple magnifying lens.
[5 MARKS]

Q.

A man who cannot see clearly beyond 5 m wants to see stars clearly. He should use a lens of focal length ___ m.

Q.

An object is placed in front of a convex lens such that the image formed has the same size as that of the object. The object is placed at:

1. F

2. Optical Centre

3. Centre of Curvature

4. 2F

Q.

State True or False:

A person with hypermetropia can see nearby objects distinctly but cannot see far away objects clearly.

1. False

2. True

Q.

A diverging lens will produce always_____

Q.

An optician advises an old man to use lenses of power +3.5 D .What defect the old man is suffering from???

Q. ntA comcave mirror of focal length f1 is placed at a distance of d from a convex lens of focal length f2 .A beam of liqht coming from infinity and falling on this convex lens mirror combination returns to infinity .The distance d be?n ntExplain in detail why does one of the two focal length get doubledn

Q. Hypermetropia can be rectified using:

1. concave lens
2. convex lens
3. cylindrical lens
4. bifocal lens

Q. ntA concave mirror of focal length f1 is placed at a distance of d from a convex lens of focal length f2. A beam of light coming from infinity and falling on this convex lens- concave mirror combination returns to infinity. The distance d must be equal ton ntA. f1+f2n ntB. -f1+f2n ntC. 2f1+f2n ntD. -2f1+f2n

Q.

A lens is called a thin lens if its overall thickness is large.

1. True
2. False

Q.

1. True
2. False

Q.

Is M = -v/u or v/u ?

Q. Choose the correct option which is true about a bi-concave lens :

1. It cannot form virtual images
2. None of the above
3. It can magnify objects
4. Its focal length is positive
5. It cannot form real images

Q. A man focused an inverted image formed by a lens. It can be:

1. Convex lens
2. Concave lens
3. Convex or concave lens
4. Plane mirror

Q. Why is concave lens called diverging lens ?

Q. Lens spectacles are made from

1. Soft Glass
2. Hard Glass
3. Pyrex Glass
4. Flint Glass

Q. An object is placed on the axis of a lens. An image is formed by refraction in the lens. For all positions of the object on the axis of the lens, the positions of the image are always between the lens and the object. (a) name the lens. (b) Draw a ray diagram to show it. (c) State three characteristics of the image.

Q. A lens which is thinner at the middle and thicker at the edges is called a :

1. Concave lens
2. Cylindrical lens
3. Convex lens
4. None of these

Q. When rays of light fall on a convex lens, it

1. Converges them
2. Does not bend them
3. Diverges them
4. Enlarges them

Q. A parallel beam of light rays travelling parallel to principal axis after passing through the lens actually meet. This phenomena happens for which type of lens?

1. Concave
2. Bipolar
3. Convex
4. Cylindrical

Q. A concave lens is a divergent lens and is used in projectors

1. True
2. False

Q.

When an object is placed at a distance of 5 cm in front of a convex mirror of focal length 10 cm, then:

1. v = + 33cm

2. v = + 3.3cm

3. v = - 33cm

4. v = - 3.3cm

Q. ............... lens is known as diverging lens.

1. Convex
2. Concave
3. Sperical
4. Plano convex

Q. Does an air bubble inside water behave like a lens? If so, what type of lens is it? Explain?

Q. Write the differences between convex and concave lens.