IGCSE Physics Paper-1: Specimen Questions with Answers 106 - 107 of 109
Question number: 106
Question
A small amount of a radioactive isotope contains 72 billion unstable nuclei. The half-life of the isotope is 4 hours. How many unstable nuclei would remain after 12 hours?
Choices
| Choice (4) | Response | |
|---|---|---|
| a. | 9 billion |
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| b. | 6 billion |
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| c. | 24 billion |
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| d. | 18 billion |
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Answer
a.Explanation
The life time of nuclei is can be calculated as,
Here are given,
Question number: 107
Question
Three rays of light fall on a converging lens as shown.
Rays of Light Fall on a Converging Lens.
Rays of light fall on a converging lens is shown in figure.
Which diagram shows the path of the rays after passing through the lens?
Choices
| Choice (4) | Response | |
|---|---|---|
| a. |  Figure of Falling and Reflecting Rays through the Lens. Choice A In figure path of the rays after passing through the converging lens is shown. |
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| b. |  Figure of Falling and Reflecting Rays through the Lens Choice B In figure path of the rays after passing through the converging lens is shown. |
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| c. |  Shows Figure of Falling and Reflecting Rays through the Lens. In figure path of the rays after passing through the converging lens is shown. |
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| d. |  Figure of Falling and Reflecting Rays through the Lens Choice D In figure path of the rays after passing through the converging lens is shown. |
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Answer
c.Explanation
When parallel rays incident on the converging lens, they will reflected and converged at a point another side of the lens. The distance from the converging lens to intersecting point is equal to focal length of the lens. This proper arrangement is shown in choice C.