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Answer the following.
Both students i.e. Student 1 and Student 2, had an intention of stargazing at night and knew that a…
Both students i.e. Student 1 and Student 2, had an intention of stargazing at night and knew that a telescope would be required for viewing distant stars. Student 1 visited a shop to purchase the necessary equipment for stargazing and purchased two lenses X and Y, the former being thicker and the latter thinner. On the other hand, Student 2 opted for a different approach. He decided to build his telescope by combining a concave mirror of focal length $25\text{ cm}$ and a plane mirror, along with a convex lens of focal length $5\text{ cm}$.
What is the length of the telescope of Student 1 when the final image is formed at infinity, assuming she uses the same eyepiece as Student 2 but achieves twice the magnifying power?
Answer
Answer
Official answer keyMagnifying power of telescope of student 2 $= \frac{f_0}{f_e} = 5$
Hence, the magnifying power of the telescope of student 1 = 10. Since $f_e = 5$ cm, hence $f_0 = 50$ cm.
Length = 50 + 5 = 55 cm.
Final answer: 55 cm
From ISC 2025 Practice Physics, question 67(c).
Check your working with the Lens and mirror calculator: image distance, magnification and nature for any lens or mirror, with the ray diagram.
Check your working with the Physics formula calculator: about 145 ISC Physics formulas: fill in what you know, with units, and get the rest.