Question

A 2.45 cm tall object is placed in 33.7 cm in front of a convex lens. The focal length

Answer 1

Answer:

-1.65

Explanation:

First of all, we find the position of the image by using the lens equation:

$\frac{1}{f}=\frac{1}{p}+\frac{1}{q}$

where:

f is the focal length of the lens

p is the distance of the object from the lens

q is the distance of the image from the lens

For the lens in this problem:

f = 21.0 cm (the focal length of a convex lens is positive)

p = 33.7 cm

Solving for q, we find the position of the image:

$\frac{1}{q}=\frac{1}{f}-\frac{1}{p}=\frac{1}{21.0}-\frac{1}{33.7}=0.0179 cm^{-1}\\q=\frac{1}{0.0179}=55.7 cm$

Then, the magnification of the image is given by:

$M=-\frac{q}{p}$

And substituting,

$M=-\frac{55.7}{33.7}=-1.65$

Which means that the image is inverted (negative sign) and enlarged (because M is larger than 1).