Energy and Light Summary notesWhat is Energy?

The simplest definition of energy is "the ability to do work". Energy is how things change and move. It's everywhere around us and takes all sorts of forms. It takes energy to cook food, to drive to school, and to jump in the air.

Different forms of Energy

There are 8 different forms of energy. These are shown in the table below.

Chemical energy

Chemical energy comes from atoms and molecules and how they interact.

Electrical energy

Electrical energy is generated by the movement of electrons.

Heat energy Heat energy is also called thermal energy. It comes from molecules of different temperatures interacting

Kinetic energy Anything that is moving has energy. Moving energy is called kinetic energy.

Light energy Light is called radiant energy. The Earth gets a lot of its energy from the light of the Sun.

Potential energy

Potential energy is energy that is stored. One example of this is a spring that is pressed all the way down.

Nuclear energy Huge amounts of nuclear energy can be generated by splitting atoms.

Sound energy Energy that travels through vibrating particles and can be picked up by our ears.

Units of Measure for Energy

In physics, the standard unit of measure for energy is the joule which is abbreviated as J. Named after the English scientist James Joule who studied energy in the 1800s.

There are other units of measure for energy that are used throughout the world including kilowatt-hours, calories, newton-meters, therms, and foot-pounds.

Law of Conservation of Energy

This law states that energy is never created or destroyed, it is only changed from one state to another. One example is the chemical energy in food that we turn into kinetic energy when we move.

Energy transformers

Energy is transformed from one type to another constantly all around us. Below are some examples of energy transformations in everyday life.

Fossil Fuels

Our main sources of energy for hundreds of years have been fossil fuels. They are called fossil fuels because they are made from decaying fossils such as sea crustaceans or decaying vegetation.

They take millions of years to create (under extreme pressure and temperatures),which is why we are running out of fossil fuels. For this reason they are often callednon-renewable sources of energy.

Coal, oil and natural gas are the three main fossil fuels we extract from the Earth.Problems with fossil fuels

We are polluting our atmosphere with greenhouse gases. When fossil fuels areburned they release carbon dioxide which contributes to global warming. This is because carbon dioxide traps heat in our atmosphere preventing it from leaving, as a result the temperature of the planet increases damaging the environment and wildlife as well as causing serious problems for people.

Other pollutants such as sulphur dioxide are also given off, this poisonous gas dissolves in rain clouds to produce acid rain. Acid rain damages trees and plants and is washed into lakes and rivers turning them acidic. These have serious impact on wildlife.

Alternative and cleaner energy sources are needed!

Renewable energies

A renewable energy source is one that can be replenished. This means the source can be used over and over again without running out. Examples of this include hydropower from turbines in a dam, wind power from windmills, and solar power from the sun.

The Wind Turbine

Wind turbines are able to harness the power of the wind to generate electrical energy. The wind pushes against the blades of the turbine which cause it to turn. The turbine has generator inside it which produced electricity when turned. Wind power will never run out, so it is a renewable source of energy.

Wind turbines should be located in windy areas like Scotland. Although if it gets toowindy, the turbines must be shutdown to avoid damaging them.Wind turbines do not give off any dangerous greenhouse gases so are consideredclean forms of generating electrical energy.

Wave Power

Wave power stations use the energy of the wave to move a piston or turbine whichgenerates electrical energy. Wave power will never run out, so it is a renewable source of energy.

In the same way that wind causes a turbine to turn, the waves move the turbine or piston, which is connected to a magnet surrounded by coils of wire. As the magnet moves through the coils electrical energy is generated.

Wave power stations must be located in the sea or areas of water that get a lot of waves. Normally they are located close to the shore.

Wave power stations do not give off any dangerous greenhouse gases so are considered clean forms of generating electrical energy.

Hydroelectric Power

Hydroelectric energy uses the kinetic energy of falling water to spin a turbine which generates electrical energy. Hydro electric energy will never run out, so it is a renewablesource of energy. Rainwater collects in a raised reservoir with a dam to stop the water flowing downstream. This water is high up so has a lot of potential energy.

When operational the water is allowed to flow down the dam through turbinesthat are connected to a magnet surrounded by coils of wire. The magnetmoves through the coils and electrical energy is generated.

There are two main energy changes involved with hydroelectric power stations.

1. As the water flows down the dam the potential energy of the water turns into kinetic energy

2. Then the kinetic energy of the water turns the turbine changing kinetic energy into electrical energy.

The location of hydroelectric power stations is very important. They must be built inhilly areas so that water can be stored in a raised reservoir. Normally they are builtin areas that receive a lot of rain to fill the reservoir and in rural areas far awayfrom cities and towns. Fortunately for us Scotland is perfect for hydroelectric powerstations.

Hydroelectric power stations do not give off any dangerous greenhouse gases soare considered clean forms of generating electrical energy.

Solar Cell

Solar panels are made up of 30 or more solar cells joined together. They generate electrical energy by using the energy found in sunlight to move electrons in the panel. Solar power will never run out, so it is a renewable source of energy.

Solar power is very useful in areas that receive a lot of daylight and is normally sunny. The more sunlight that strikes the solar cells the greater the electrical energy generated.

Solar cells do not give off any dangerous greenhouse gases so are considered clean forms of generating electrical energy.

Overview of advantages and disadvantages of renewable energy compared

with fossil fuels.

Light

Light is a form of energy made of photons. Light is unique in that it behaves like both a particle and a wave.

Light is emitted from luminous sources such as the sun.

Rays of light always travel in straight lines that move very quickly (300,000,000 meters per second).

Reflection

When a single ray of light hits a plane mirror at an angle it will reflect off the mirrorat the same angle.

Law of reflection: Angle of incidence = Angle of reflection

Light reflecting off non-luminous objects is how we are able to see most things.

Refraction

When a single ray of light passes straight through a rectangular block it does notchange direction but it does change speed (this cannot be seen but the ray of lightwill slow down).

When a single ray of light passes through a rectangular block at an angle itrefracts. This means the ray of light changes speed (slows down) and changesdirection as can be seen below.

Convex and Concave lenses

Lenses refract light, they have wide range of uses from glasses to telescopes and microscopes.There are two main types of lenses.Convex lenses (converging lenses) will cause the rays to converge to a focus.

Concave lenses (diverging lenses) will cause the rays to spread out (diverge). The rays will not come to a focus.

White light

When white light passes through a triangular prism it splits up into 7 differentcolours called the visible spectrum. This tells us that white light is actually madeup of these colours.

The same thing happens when white light from the sun passes through rain drops.It splits up into the 7 different colours of the visible spectrum (otherwise known tonon-scientists as a rainbow).

The Electromagnetic spectrum

The electromagnetic is a group of energy waves that travel at the speed of light. Electromagnetic waves are classified according to their frequency. The different types of waves have different uses and functions in our everyday lives. The most important of these is visible light, which enables us to see.

Radio Waves

Radio waves have the longest wavelengths of all the electromagnetic waves. They range from around a foot long to several miles long. Radio waves are often used to transmit data and have been used for all sorts of applications including radio, satellites, radar, and computer networks.

Microwaves

Microwaves are shorter than radio waves with wavelengths measured in centimeters. We use microwaves to cook food, transmit information, and in radar that helps to predict the weather. Microwaves are useful in communication because they can penetrate clouds, smoke, and light rain. The universe is filled with cosmic microwave background radiation that scientists believe are clues to the origin of the universe they call the Big Bang.

Infrared

Between microwaves and visible light are infrared waves. Infrared waves are sometimes classified as "near" infrared and "far" infrared. Near infrared waves are the waves that are closer to visible light in wavelength. These are the infrared waves that are used in your TV remote to change channels. Far infrared waves are further

away from visible light in wavelength. Far infrared waves are thermal and give off heat. Anything that gives off heat radiates infrared waves. This includes the human body!

Visible light

The visible light spectrum covers the wavelengths that can be seen by the human eye. This is the range of wavelengths from 390 to 700 nm which corresponds to the frequencies 430-790 THz.

Ultraviolet

Ultraviolet waves have the next shortest wavelength after visible light. It is ultraviolet rays from the Sun that cause sunburns. We are protected from the Sun's ultraviolet rays by the ozone layer. Some insects, such as bumblebees, can see ultraviolet light. Ultraviolet light is used by powerful telescopes like the Hubble Space Telescope to see far away stars.

X-rays

X-rays have even shorter wavelengths than ultraviolet rays. At this point in the electromagnetic spectrum, scientists begin to think of these rays more as particles than waves. X-rays were discovered by German scientist Wilhelm Roentgen. They can penetrate soft tissue like skin and muscle and are used to take X-ray pictures of bones in medicine.

Gamma rays

As the wavelengths of electromagnetic waves get shorter, their energy increases. Gamma rays are the shortest waves in the spectrum and, as a result, have the most energy. Gamma rays are sometimes used in treating cancer and in taking detailed images for diagnostic medicine. Gamma rays are produced in high energy nuclear explosions and supernovas.