Question

You’ve been asked to build a telescope from a $2.0x$magnifying lens and a $5.0x$magnifying lens.

a. What is the maximum magnification you can achieve?

b. Which lens should be used as the objective? Explain.

c. What will be the length of your telescope?

Short answer

a. The maximum magnification is$M_{max}=2.5$.

b. The lens should be used as the objective is$L\le f_R=f_L$.

c. The length of the telescope is$L=7$.

Step-by-step solution

Part (a) Step 1: Given Information.

We need to find out the maximum magnification to achieve.

Part(a) Step 2 : Simplify

Maximum magnification:

$$\begin{gathered} M_{max}=\frac{f_{obj}}{f_{obj}} \\ {M}_{max}=\frac{5}{2} \\ {M}_{max}=2.5 \end{gathered}$$.

Part (b) Step 1 : Given Information.

We need to find which lens should be used as the objective.

Part (b) Step 2: Explanation.

As we know that the distance between eyepiece and objective lenses are lightly less than to their focal length.

$L\le f_R+f_L$.

Part (c) Step 1 : Given Information.

We need to find the length of the telescope.

Part (c) Step 2: Calculation.

Length of telescope is:

$$\begin{gathered} L=f_R+f_L \\ L=5+2 \\ L=7 \end{gathered}$$.