Question

A converging lens has a focal length of 14.0cm. For an object to the left of the lens, at distances of 18.0cm and 7.00cm, determine:

a. The image position
b. The magnification
c. Whether the image is real or virtual
d. Whether the image is upright or inverted

Answer 1

Step-by-step explanation:

A converging lens id also known as a convex lens. A convex lens has a positive focal length.

Using the lens formula to determine the image distance from the lens for each object distance.

1/f = 1/u + 1/v

f = focal length

u = object distance

v = image distance

For an object placed at distance of 18.0cm with focal length 14.0cm,

1/v = 1/f-1/u

1/v = 1/14 - 1/18

1/v = 9-7/126

1/v = 2/126

v = 126/2

v = 63cm

Since the image distance is positive for an object 18cm from the lens, the image formed by the object at this distance is a real and inverted image.

The magnification = v/u = 63/18 = 3.5

Similarly for an object placed at distance of 7.0cm with focal length 14.0cm,

v = uf/u-f

v = 7(14)/7-14

v= -14.0 cm

Since the image distance is negative for an object placed 7.0 cm from the lens, the image formed by the object at this distance is a virtual and upright image.

The magnification = v/u = 14/7 = 2

Note that the negative value is not taken into account when calculating magnification. The negative value only tells us the nature of the image formed.