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Questions and Answers
What is the power of the combination of a convex lens of focal length 25 cm placed coaxially in contact with a concave lens of focal length 20 cm?
What is the power of the combination of a convex lens of focal length 25 cm placed coaxially in contact with a concave lens of focal length 20 cm?
- -1.25 D, diverging (correct)
- -5 D, converging
- -0.20 D, diverging
- 0.20 D, converging
For a glass lens of refractive index 1.5 placed in a trough of liquid, what must be the refractive index of the liquid in order to make the lens disappear?
For a glass lens of refractive index 1.5 placed in a trough of liquid, what must be the refractive index of the liquid in order to make the lens disappear?
- 0.5
- 1.0
- 2.0
- 1.5 (correct)
What is the focal length of a combination of a converging lens kept coaxially in contact with a diverging lens, both of equal focal lengths?
What is the focal length of a combination of a converging lens kept coaxially in contact with a diverging lens, both of equal focal lengths?
- Twice the focal length of individual lenses
- Zero
- Equal to the focal length of individual lenses
- Infinity (correct)
An astronomical telescope uses two lenses of powers 10 D and 1 D. What is its magnifying power in normal adjustment?
An astronomical telescope uses two lenses of powers 10 D and 1 D. What is its magnifying power in normal adjustment?
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What are the necessary conditions for the phenomenon of total internal reflection to occur?
What are the necessary conditions for the phenomenon of total internal reflection to occur?
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