Question

An object is 16.0cm to the left of a lens. The lens forms an image 36.0cm to the right of the lens.

a)What is the focal length of the lens?

b)Is the lens converging or diverging?

c)If the object is 8.00mm tall, how tall is the image?

d)Is it erect or inverted?

Answer 1

a. Let f be the focal lenght. Formula for lens focal lenght is : 1/v + 1/u = 1/f ; where u is the distance of object and v is the distance of image.
u = 16.0 cm
v = 36.0 cm
1/f = 1/16 + 1/36
f = 11.1 cm

b. Since focal lenght is positive. Therefore the lens is converging.

c. Magnification is M = -v/u = -32/16 = -2.25 ; for the object being talked above.
Height of Image = M*(Height of object) = -2.25*8.00mm = -18.0mm

d. Since M is less than 0. Therefore Image is Inverted.