The distance between an object and the screen is 100cm. A lens placed between them produces an image on the screen when the lens is placed at two positions 40cm apart. The power of the lens is nearly:
Correct answer: B. 5 diopters
- A. 3 diopters
- B. 5 diopters
- C. 7 diopters
- D. 9 diopters
Explanation
The lens power can be calculated using the formula: Lens Power = 1/f, where f is the focal length of the lens. In this case, since the lens is placed at two positions 40cm apart, it means the lens is moved 40cm from its initial position. This change in position corresponds to a change in the image distance, which allows us to calculate the focal length and subsequently the lens power. A lens power of 5 diopters is the correct answer as it satisfies the conditions provided in the question. Options 3 diopters, 7 diopters, and 9 diopters do not match the calculated value and are incorrect.
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Light is studied through reflection, refraction, dispersion, interference, diffraction and polarization, linking ray behavior with its wave nature. Questions may involve mirrors, lenses, optical instruments, refractive index and image formation, while geometrical optics deals with rays and wave optics explains effects such as interference and diffraction.
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