IGCSE Physics Paper-1: Specimen Questions with Answers 106 - 108 of 149

Question 106

Question

MCQ▾

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)

a.

9 billion

b.

6 billion

c.

24 billion

d.

18 billion

Answer

a.

Explanation

The life time of nuclei is can be calculated as,

Here are given,

Question 107

Question

MCQ▾

Three rays of light fall on a converging lens as shown.

Rays of Light Fall on a Converging Lens

Which diagram shows the path of the rays after passing through the lens?

Choices

Choice (4)

a.

Figure of Falling and Reflecting Rays through the Lens. Choice A

b.

Figure of Falling and Reflecting Rays through the Lens Choice B

c.

Shows Figure of Falling and Reflecting Rays through the Lens

d.

Figure of Falling and Reflecting Rays through the Lens Choice D

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.

Question 108

Question

MCQ▾

An electromagnet is used to separate magnetic metals from no-magnetic metals. Why is steel unsuitable as the core of the electromagnet?

Choices

Choice (4)

a.

It has a high thermal capacity

b.

It forms a permanent magnet

c.

It is good conductor of electricity

d.

It has a high density

Answer

b.

Explanation

In electromagnet when we remove current the magnetic field should be removed. But if we take steel as the core of the electromagnet and starts the current the steel will magnetized and although current will off, the steel will be permanent magnet.

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