1. Use Rayleigh criterion for a telescope

For a circular aperture, the minimum angular resolution is

$\theta_{\min} = 1.22\frac{\lambda}{D}$

where:

• $\lambda = 5500\,\text{\AA} = 5500 \times 10^{-10}\,\text{m} = 5.5 \times 10^{-7}\,\text{m}$
• $D = 5\,\text{m}$

So,

$\theta_{\min} = 1.22\frac{5.5\times 10^{-7}}{5}$

$\theta_{\min} = 1.22 \times 1.1 \times 10^{-7}$

$\theta_{\min} \approx 1.34 \times 10^{-7}\,\text{rad}$

2. Relate angular resolution to linear separation on the moon

If two objects on the moon are just resolved, their minimum linear separation is

$s = L\theta_{\min}$

Given distance from earth to moon:

$L = 4\times 10^5\,\text{km} = 4\times 10^8\,\text{m}$

Hence,

$s = 4\times 10^8 \times 1.34\times 10^{-7}$

$s \approx 53.6\,\text{m}$

3. Choose the closest option

$s \approx 54\,\text{m}$

This is closest to $60\,\text{m}$.

4. Option check

• A: 20 m — too small
• B: 200 m — too large
• C: 600 m — much too large
• D: 60 m — closest and correct

Therefore, the correct answer is D.