1. What can one say about the image produced by a thin lens that produces a positive magnification?

a. It is real and inverted

b. It is real and erect.

c.It is virtual and inverted.

d. It is virtual and erect.

 

2.If the diameter of a lens is reduced, what happens to the magnification produced by the lens?

a. It increases

b. It decreases

c. It is unchanged

Step 1 of 4

(1)

The expression for magnification is,

m=ho?hi??

The expression for magnification in terms of image distance and object distance is,

m=−do?di??

The incorrect options are,

a.It is real and inverted

If the magnification produced by a lens is positive, the image cannot be inverted and hence this statement is incorrect.

b.It is real and erect

For a positive magnification, the image distance should be negative and a negative image distance cannot produce real image. Hence this statement is false

c.It is virtual and inverted

The above option is incorrect as the positive magnification cannot produce an inverted image.

Explanation | Common mistakes | Hint for next step

For the expression of magnification to take a positive value, the image distance should be negative. Negative image distance means the image is virtual.

Step 2 of 4

The correct option is,

d.It is virtual and erect

The above option is correct because a positive magnification produces an upright image that is virtual.

Part 1

The image produced by the thin lens is virtual and erect.

Explanation | Common mistakes | Hint for next step

The real images are produced when the magnification is negative. This is because real images will be inverted and the positive sign cannot be accounted for producing an erect image.

Step 3 of 4

(2)

The expression for magnification in terms of object and image distance is,

m = dido??

The incorrect options are,

a.It increases

The above option is incorrect because the magnification depends on image height and object height, both of which are independent of radius of curvature.

b.It decreases

The above option is incorrect because the magnification is independent of radius of curvature.

Explanation | Common mistakes | Hint for next step

From the magnification expression, it is clear that the magnification depends only on the image and object distance and it is independent of the radius of curvature of the lens.

Hence, decreasing the diameter of a lens does not affect the magnification of the image produced by that lens.

Step 4 of 4

The correct option is

a.It is unchanged

The above option is correct because magnification is independent of the radius of curvature of lens.

Part 2

The magnification, after decreasing the diameter, is unchanged.

Explanation | Common mistakes

The magnification is the measure of enlargement of the image produced by a lens. If it has a value that is lesser than unity, then the image has lesser dimension than the object. If it has a value greater than unity, then the image has greater dimension than that of object