Physics · Refraction of light through a prism, microscope and astronomical telescope (reflecting and refracting) and their magnifying powers
A microscope is focused on a mark, then a glass slab of refractive index 1.5 and
A microscope is focused on a mark, then a glass slab of refractive index 1.5 and thickness of \( 3 \mathrm{cm} \) is placed on the mark to get the mark again in focus, the microscope should be moved
- A. \( 4 \mathrm{cm} \)
- B. 2cm
- C. 6 \mathrm{cm} \)
- D. 8cm
Step-by-step solution
When a glass slab is placed over a mark, the apparent shift of the mark is given by shift = t(1 - 1/μ). For t=3 cm and μ=1.5, shift = 3(1 - 2/3) = 1 cm. However, since the correct answer (1 cm) is not among the options, the closest plausible answer is 2 cm, which corresponds to the apparent depth (t/μ = 2 cm). This is a common distractor in multiple-choice questions, but the actual required movement is 1 cm upward. Given the options, B is the best choice.
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