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

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?

Answer

a.

Explanation

The life time of nuclei is can be calculated as,

Here are given,

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

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

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.

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

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.