What is the brain?

The brain is an organ inside the skull.
It forms only about two per cent of our
bodyweight, but it controls our feelings,
movement, skills and every function necessary
to live. The human brain is divided into three
major parts; the cerebrum, the cerebellum,
and the brainstem. The cerebrum gives us
intelligence. It makes up 85 per cent of the
brain and operates voluntary muscles that we
have control over. The cerebrum is the area
of the brain that allows us to dance, jump
or solve puzzles. It also stores information,
which we call memory. The cerebellum or
‘little brain’ is below the cerebrum and is
just one-eighth of the size of it. The
cerebellum controls balance and tells the
muscles how to move. The brainstem
connects the rest of the brain to the spinal
cord, which runs down the neck and back.
The brainstem controls involuntary muscles
that work without us thinking about it, like
the heart, the lungs and the stomach.

TODAY MY WALLPAPER

What is the range of sound that the human ear can catch?

A young human being
can hear almost all
sounds from 15 Hz to
20,000 Hz. With age,
you hear less, and find
it difficult to catch
higher frequencies. A
human voice carries
sound at about 60 Hz,
but a shout can reach
13,000 Hz. Elephants,
dogs and other animals
can hear ultrasonic
sound that we cannot.

How does ultrasonic sound help doctors?

Ultrasonic sound waves
help doctors locate
and diagnose medical
problems, because
different tissues reflect
sound waves in
different ways. Using
this method, doctors
can also monitor the
development of a
foetus during pregnancy.

How do I speak?

Human beings have
vocal chords inside the
larynx which produce
sound. When air passes
through a gap between
the chords, these
chords vibrate and
produce a sound.
All animals that can
produce a sound have
vocal chords, except
birds which produce
sound through a bony
ring, called a syrinx

Can you measure sound?

Sound is measured in several ways:
frequency, wavelength and amplitude. Sound
waves vibrate at different rates. These are
called frequencies, measured in cycles per
second or Hertz (Hz). 1 Hertz = 1 vibration
per second. A wavelength measures the
length of one cycle. Longer wavelengths
have a lower pitch. The lowest tones that a
human can catch are about 16 vibrations
per second, or 16 Hz. Amplitude measures
how loud the sound is. A sound wave of high
amplitude will produce a
louder sound. It is measured
in decibels (Db).

How does sound move?

Sound needs a medium like air, water or
solids to travel through. When something
moves through the air, it disturbs the
molecules of gas in the air around it. The air
vibrates or moves back and forth. This
vibration is heard as sound. The greater the
vibration, the louder the sound. Since sound
travels in waves, it gets weaker the further it
travels. That is why your voice cannot be
heard beyond a certain distance. If you put in
more energy and shout, the sound waves will
be stronger and travel further so that your
voice can be heard further. Sound cannot
travel through a vacuum, because a vacuum
is completely empty, and has no medium
with which to carry the sound wave.

Sound?

Sound is a form of energy that is transferred by pressure waves
in air or through other materials. These waves can be picked up
by the ear, which is how we hear sounds. But there are many
sounds around us that our ears do not pick up, and so we do
not hear them.

Why is the sky blue?

The Earth’s atmosphere contains tiny
molecules of gas and dust particles. Sunlight
entering the atmosphere hits these molecules
and dust particles. Colours with longer
wavelengths, like red and yellow, can pass
through the atmosphere without being
scattered by these molecules of gas and dust
particles. But the colour blue, with its shorter
wavelength, is scattered by the gas molecules
and the dust in the upper atmosphere. This is
why the sky appears blue.

Blue water
Water is actually colourless. However, large amounts of
water act like the sky and scatter blue light. This is why
seas, lakes and rivers usually appear blue.

How are rainbows formed?

A rainbow is created by the refraction of
sunlight by water droplets in the atmosphere.
When sunlight passes through a drop of water,
it is bent in such a way that the various colours
that make up white light are split. Each colour
is bent at different angles. Red bends the
least, while violet is bent the most. It is this
phenomenon that we see as a rainbow.

A rainbow of colours
The rainbow is always formed on that portion of the sky
that is directly opposite to the Sun. A rainbow is not
composed of just seven colours. In fact, it also contains
colours like infrared that cannot be seen.

Glass is also a solid object, yet how are we able to see through it?

The molecules of solid matter are usually
packed tightly together, and therefore do not
allow light to pass through them. In liquids
and gases, the molecules move about freely
and there is a lot of space between them.
That is why light is able to pass through these
materials easily. Glass is made by first melting
sand, and then cooling it. The substance made
has the rigidity of a solid, but still has the free
moving molecules of a liquid. So the space
between the molecules of glass allows light to
pass through, although glass itself is a solid.

What do the words ‘opaque’ and ‘transparent’ mean?

Solids are said to be
opaque, as they do
not allow light to pass
through them, while
water and glass are
transparent as light is
able to pass through.