Question 156: Ray Optics

Question

The graph shows how the magnification m produced by a thin lens varies with image distance v. What is the focal length of the lens used?

Accepted Answer

As the graph between magnification (m) and
image distance (v) varies linearly, then
m = k
1
v + k
2
$$ \Rightarrow {v \over u} = {k_1}v + {k_2}$$
$$ \Rightarrow {1 \over u} = {k_1} + {{{k_2}} \over v}$$
$$ \Rightarrow {{{k_2}} \over v} - {1 \over u} = {k_1}$$
Clearly, $${k_1} = {1 \over f}$$ and  k
2
= 1 here
$$ 	herefore f = {1 \over {slope\,of\,m - y\,graph}} = {b \over c}$$

Answer

$${{{b^2}} \over {ac}}$$

Answer

$${{{b^2}c} \over a}$$

Answer

$${a \over c}$$

Answer

$${b \over c}$$

Ray Optics

The graph shows how the magnification m produced by a thin lens varies with image distance v. What is the focal length of the lens used?

Choose the correct answer: