Childrens Illustrated Encyclopedia

427

Mutant house fly

Some elementS give out invisible particles called radiation. Substances

that produce radioactivity are described as radioactive. Radioactivity comes out

of the central part (the nucleus) of atoms of a radioactive substance and carries

away energy from inside atoms. this energy can be both useful and harmful;

it can be used to generate electricity or to create enormous

explosions. A radioactive substance, such as uranium,

is made up of big, unstable atoms. Some of the

particles that form the atoms break off and

are radiated as alpha particles or beta

particles, or as gamma rays.

eventually atoms reach a

stable state—stop

decaying—and

the substance is no

longer radioactive. this process

can take millions of years.

typeS of RAdioActivity

Radioactive substances give off three types

of radiation: alpha, beta, and gamma.

Alpha particles are larger than those of

beta radiation, so cannot penetrate as far.

gamma radiation is a very high frequency

wave and can pass through most materials.

only direct collisions with atoms can stop

it. Shields to protect people from gamma

radiation are made from dense material,

such as lead.

deep-SpAce nucleAR geneRAtoRS

Spacecraft that visit regions of the solar system far

from the sun can’t use solar panels to generate

power because they don’t get enough sunlight.

instead, these probes often take along a small

block of radioactive plutonium, which generates

heat that is converted into useful electricity.

the new Horizons probe, shown here before

launch, carries its plutonium well protected

inside the black cylinder seen on the left.

gene mutAtion

Alpha and beta particles,

x-rays, and gamma rays

produced by radioactivity can

damage living things, because

they alter the dnA of genes.

this can result in life-

threatening diseases such as

cancer. it can also lead to

mutations, or changes,

in the next generation.

SourceS of radioactivity

Earth’s rocks are naturally

radioactive as they contain

radioactive substances from

when our planet formed.

In this laboratory

experiment, a radioactive

substance emits radiation

through a small hole in its

lead casing.

The explosion of a nuclear

weapon produces both

electromagnetic (light) and

radioactive radiation, with

devastating effects.

In a nuclear power station,

the heat produced by

radioactivity is used to

make steam and drive

an electricity generator.

Radon is a naturally

occurring radioactive

gas that seeps out of the

ground in some parts of

the world, such as these

hot springs.

geigeR counteR

A geiger counter consists of a

gas-filled tube and a meter.

it can detect radioactivity.

High-frequency

gamma radiation

wave

Radioactivity

Radiation damage has

caused this rare mutation

of yellow eyes.

Gamma

radiation

mARie cuRie

polish-born scientist marie curie

(1867-1934), and her husband,

pierre, won the 1903 nobel

physics prize for discovering

radioactivity. She did not know

that it was harmful and died

from radiation poisoning.

Large alpha particle

Small beta particle

Alpha

radiation

Beta

radiation

Atoms and molecules

genetics

nuclear energy

X-rays

Find out more

New Horizons probe uses

radioactive plutonium to

generate power.

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