Question 7: Ray Optics

Question

A simple telescope, consisting of an objective of focal length $$60 \mathrm{~cm}$$ and a single eye lens of focal length $$5 \mathrm{~cm}$$ is focused on a distant object in such a way that parallel rays emerge from the eye lens. If the object subtends an angle of $$2^{\circ}$$ at the objective, the angular width of the image is

Accepted Answer

For telescope
It is a case of normal adjustment.
Hence, $$M=\frac{f_o}{f_e}$$ also $$M=\beta / \alpha$$
Therefore, $$\frac{\beta}{\alpha}=\frac{f_o}{f_e}$$
Here $$f_o=60 \mathrm{~cm}, f_e=5 \mathrm{~cm}$$
$$\begin{aligned}
& \alpha=2^{\circ} \
	ext { Hence, } \quad & \beta=24^{\circ}
\end{aligned}$$

Answer

$$10^{\circ}$$

Answer

$$24^{\circ}$$

Answer

$$50^{\circ}$$

Answer

$$\frac{1}{6}^{\circ}$$

Ray Optics

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