CIE Physics Paper-1: Specimen Questions 106 - 107 of 109

Question number: 106

MCQ▾

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

b.

6 billion

c.

18 billion

d.

24 billion

Answer

a.

Explanation

The life time of nuclei is can be calculated as,

A=A0e(0.693)tT12

Here A0=72billion,t=12hours,T12=4hours are given,

A=72×e(0.693)124

A=9billion.

Question number: 107

MCQ▾

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.

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

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.

b.
Figure of falling and reflecting rays through the lens choice 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.

c.
shows figure of falling and reflecting rays through the lens.

shows figure of falling and reflecting rays through the lens.

In figure path of the rays after passing through the converging lens is shown.

d.
Figure of falling and reflecting rays through the lens choice 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.

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.

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