2. • The best we can come up with is that energy is the ability of a
system to do work.
• If you stretch a rubber band, you're storing elastic potential
energy in the band, and when you let go, it springs back,
releasing that energy again. You gave the rubber band the
ability to do work - the ability to move, and so it did.
• Work is a force applied over a distance. So having energy
allows you to apply forces and cause something to move a
distance.
• If you want to move a piano across the room, you better have
eaten in the last few days, because you need energy to do it.
Let's take a closer look at a few particular forms of energy:
thermal, radiant, chemical, electric and nuclear.
3. Radiant Energy
• Radiant energy is the energy of electromagnetic waves.
• It is a form of energy that can travel through space.
• For example, we receive the heat from the sun, which is located very
far from the earth via radiation. The sun's heat is not transmitted
through any solid medium, but through a vacuum.
• This is possible by electromagnetic waves.
Electromagnetic waves
• Each time static energy from electric and magnetic force come
together, they induce an electric field around them.
An example of electric static force is the shock you get when you
hold a metal door knob.
4. • An example of a magnetic force is the pull that attracts metals to the
magnet.
• Now, the electrical field induced causes waves, called
electromagnetic waves, and they can travel through a vacuum (air),
particles or solids.
• These waves resemble the ripple (mechanical) waves you see when
you drop a rock into a swimming pool, but with electromagnetic
waves, you do not see them, but you often can see the effect of it.
• The energy in the electromagnetic waves is what we call radiant
energy.
• There are different kinds of electromagnetic waves and all of them
have different wavelengths, properties, frequencies and power, and
all interact with matter differently.
• The entire wave system from the lowest frequency to the highest
frequency is known as the electromagnetic spectrum.
• The shorter the wavelength, the higher its frequency and vice versa.
White light, for example, is a form of radiant energy, and its
frequency forms a tiny bit of the entire electromagnetic spectrum.
5. How Does Radiant Energy Work?
• Electromagnetic waves can travel through outer space.
• They can travel for long distances, and they move at the speed of
light.
• Work is done by radiant energy as the electromagnetic waves
come into contact with particles and cause them to move.
• Radiant energy from the sun is specifically referred to as solar
energy.
• The sun contains a tremendous amount of radiant energy that
produces electromagnetic waves.
• These waves travel away from the sun through space and time.
When the waves come into contact with some object - let's say
our skin - they cause the molecules in our skin to move faster.
• As the molecules move faster, we feel warmer.
• Those same electromagnetic waves traveling through space don't
do any work because there isn't anything to contact.
• At the same time, there is nothing to stop the waves, so they
continue to travel until they hit something.
