Spherical Lenses

Q.

State the relationship between object distance, image distance, and focal length of a spherical mirror.

Q.

What is the magnification of concave mirror?

Q.

Why does Mercury have a convex meniscus?

Q.

Which lens is used in magnifying glass?

Q. A concave lens of focal length $f$ forms an image which is $n$ times the size of the object. The distance of the object from the lens is:

1. $(1-n)f$
2. $(1+n)f$
3. $\left(\frac{1+n}{n}\right)f$
4. $\left(\frac{1-n}{n}\right)f$

Q.

What are the 3 types of lenses?

Q.

Which type of lenses are : (a) thinner in the middle than at the edges ? (b) thicker in the middle than at the edges ?

Q.

Convex lens of very short focal length will make:

1. Lesser divergence of light rays

2. Lesser convergence of light rays

3. Higher convergence of light rays

4. Higher divergence of light rays

Q. Lens is an optically transparent medium whose one or both surfaces are spherical.

1. True
2. False

Q. Complete the diagram given below to show the formation of image of the object AB.
(a) Name the lens LL'.
(b) What are the points O and O' called?
(c) Where is the image formed?

[5 MARKS]

Q.

The diagram alongside shows a lens as a combination of a glass slab and two prisms.

(i) Name the lens formed by the combination.

(ii) What is the line XX' called ?

(iii) Complete the ray diagram and show the path of the incident ray AB after passing through the lens.

(iv) The final emergent ray will either meet XX' at a point or appear to come from a point on XX'. Label the point as F. What is this point called ?

Q. Which of the following can be used as the magnifying glass?

1. Concave mirror
2. Convex lens
3. Concave lens
4. Convex mirror

Q. How does a concave lens differ from a convex lens?

1. A convex lens is another way to describe a plane mirror whereas a concave lens is curved at the centre.
2. A concave lens is curved inward on both sides whereas a convex lens is curved only on one side.
3. A convex lens has a thick center and thin edges whereas a concave lens has a thin center and thicker edges.
4. A convex lens has a thin center and thick edges whereas a concave lens has a thick center and thinner edges.

Q.

Name the two kinds of lens. Draw diagrams to illustrate them.

Q. Choose which of the following options are correct.

1. 
2. 
3. 
4. 

Q.

State the condition for each of the following :

(a) a lens has both its focal lengths equal.

(b) a ray passes undeviated through the lens.

Q.

The minimum distance between an object and its real image formed by a convex lens is:

1. 5/2f

2. 2f

3. 4f

4. 3/2f

Q. Which of the following statements is true?

1. Concave lenses can both converge and diverge the rays falling on them.
2. Concave lenses are also called converging lenses.
3. Convex lenses are also called converging lenses.
4. Convex lenses are also called diverging lenses.

Q.

The diagram alongside shows a lens as a combination of a glass slab and two prisms.

(i) Name the lens formed by the combination.

(ii) What is the line XX' called ?

(iii) Complete the path of the incident ray AB after passing through the lens.

(iv) The final emergent ray either meets XX' at a point or apppears to come from a point on XX'. Label it as F. What is this point called ?

Q. A rod of length $10cm$ lies along the principal axis of a concave mirror of focal length $10cm$ in such a way that its end closer to the pole is $20cm$ away from the mirror. The length of the image is

1. $15cm$
2. $10cm$
3. $2.5cm$
4. $5cm$

Q.

Show by a diagram, the refraction of two light rays incident parallel to the prinicipal axis of a concave lens by treating it as a combination of a glass slab and two triangular glass prisms.

Q.

We wish to obtain same sized image of an object, using a concave mirror of focal length 15 cm. where should be the object placed from the mirror?

Q. State whether true or false:

1. True
2. False

Q.
A lens is used in a magnifying glass.

1. concave
2. convex
3. cylindrical

Q. Which of the following is correct about concave lens?

1. It is a diverging lens.
2. Image is always formed either at focus or between focus and optical centre.
3. It always forms diminished image.
4. All are correct.

Q. An illuminated object lies at a distance 1.0 m from a screen. A convex lens is used to form the image of object on a screen placed at distance 75 cm from the lens. Find : (i) the focal length of lens, and (ii) the magnification.

1. (i) 17.75 cm (ii) -3
2. (i) 19.75 cm (ii) 2
3. (i) 15.75 cm (ii) -2
4. (i) 18.75 cm (ii) -3

Q. Question 1
Which one of the following materials cannot be used to make a lens?

(a) Water
(b) Glass
(c) Plastic
(d) Clay

Q. The distance at which an object should be placed in front of a convex lens of focal length 10 cm to obtain a real image double the size of object will be:

1. 5 cm
2. 30 cm
3. 15 cm
4. 10 cm

Q.

Focal length of convex lens is 20 cm, focal length of concave mirror is 30 cm. And the separation between lens and mirror is 90 cm. If the object is placed 60 cm before lens, find out position of image formed by concave mirror?

1. 60 cm from point B

2. 60 cm from point A

3. 90 cm from point B

4. 60 cm left of lens

Q. An object placed 50 cm from a lens produces a virtual image at a distance of 10 cm in front of the lens. Draw a diagram to show the formation of image and calculate the focal length of the lens