Two thin converging lenses are placed on a common principal axis. Lens L₁ has focal length $f_{1}=12\ \text{cm}$ and lens L₂ has focal length $f_{2}=6\ \text{cm}$. The distance between the object (a candle) and the screen is fixed at $80\ \text{cm}$. Lens L₁ is positioned at a distance $x$ cm from the candle, and lens L₂ is placed further to the right at a distance $y$ cm from the candle ($y x$). The image formed by L₁ serves as the object for L₂, and a sharp image is obtained on the screen.\n\nDetermine the value of $y$ (to one decimal place) that yields a sharp image on the screen, and calculate the overall linear magnification of the two‑lens system.

Question

Two thin converging lenses are placed on a common principal axis. Lens L₁ has focal length $f_{1}=12\ \text{cm}$ and lens L₂ has focal length $f_{2}=6\ \text{cm}$. The distance between the object (a candle) and the screen is fixed at $80\ \text{cm}$. Lens L₁ is positioned at a distance $x$ cm from the candle, and lens L₂ is placed further to the right at a distance $y$ cm from the candle ($y > x$). The image formed by L₁ serves as the object for L₂, and a sharp image is obtained on the screen.\n\nDetermine the value of $y$ (to one decimal place) that yields a sharp image on the screen, and calculate the overall linear magnification of the two‑lens system.

Accepted Answer

y \approx 58.3 	ext{ cm}, \; 	ext{overall magnification } \approx 1.75

Neco Model Questions Vol1 2020 Physics Question 29

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