section review's

think critically: explain why ultraviolet radiation is not used to transmit signals to and from communications

A communication satellite takes radio waves and pings other satellites or ground stations to transmit data. Ultraviolet waves carry more energy than what is needed and ultraviolet waves could be harmful.

identity: what determines the frequency of an electromagnetic wave

An electromagnetic wave has a frequency and a wavelength associated with it and travels at the speed of light. The relationship among these wave characteristics.

explain why x-rays and gamma coming from space do not reach earth surface

As the sun's rays heat up the earth, the radiation hits the atmosphere. Then the radiation heads back to the sun.

Compare: The energy transferred by high frequency and low frequency electromagnetic waves

Change in frequency of light causes change in energy and vice versa

explain how a communications satellite is used

Communications satellites are commonly used for mobile phone signals, weather tracking, or broadcasting television programs. Communications satellites are artificial satellites that relay receive signals from an earth station and then transmits the signal to other earth stations

compare and contrast x-rays and gamma rays

Compare: They're both electromagnetic radiation. Contrast: X-rays have longer wavelength, lower frequency, and carry less energy, than gamma rays.

think critically: why does the sun emit mostly infrared waves and visible light, and earth emits infrared waves

Electromagnetic radiation is a continuous spectrum of wavelengths from thousands of kilometers to wavelengths the size of fractions of an atom. They are all the same kind of radiation - the differences are only the wavelengths.

Describe: How electromagnetic waves are produced?

Form of energy by moving charged particles. As it travels through space it moves like a wave and has a electric field and a magnetic field.

describe how an AM radio signal is used to transmit information

In an FM transmission the carrier amplitude is kept constant, while the carrier frequency changes as a function of the signal amplitude.

Describe: How electromagnetic waves are produced

In an atom there are different energy levels that the electrons can be at. When an electron goes to a lower energy level it emits electromagnetic radiation as it gives out the energy.

explain why ultraviolet radiation is more damaging to living cells than infrared waves

Infrared photons have longer wavelengths than ultraviolet protons, which means that they have less energy with which to damage cells.

describe the types of information a GPS receiver provides.

It is a global navigation satellite system that provides location and time information to a GPS receiver anywhere on near Earth.

think critically: unlike sound waves, electromagnetic waves can travel in empty space. What evidence supports this statement.

Mechanical waves must have a medium whereas, an electromagnetic wave can transmit its energy through an empty space.

compare and contrast: electromagnetic waves with mechanical waves

Some waves can transfer energy. Visible light is one example Electromagnetic waves are waves that have no medium to travel where as mechanical waves need a medium for its transmission. They can transmit energy and travel through a vacuum.

describe how a cordless phone is different from a cell phone.

The base station is connected directly to a home's phone landline by a standard phone cord. ... It then broadcasts that information directly to and from the cordless phone. A cordless phone will not work if it is outside of the range of the base station. Cellular phones exchange voice data with a cellular data tower.

Describe how infrared detectors on satellites can be used to obtain information about the location of vegetation on earths surface

The satellite is when an observer looks at it from the Earth. The other interpretation is how the satellite figures out what its own location is, relative to the Earth.

explain how the energy of electromagnetic waves changes as the wavelength of the waves increases.

This is why UV radiation which has a very small wavelength has more energy than visible radiation, and this is also why UV radiation causes damage to living things.

identify: What determines the frequency of an electromagnetic wave

When an electron moves from one energy state to a state with less energy. The energy of the photon is just the change in energy of the electron.

compare: The energy transferred by high-frequency and low frequency electromagnetic waves

higher frequency visible light and has even shorter wavelengths. Lower frequency is a radio frequency between medium frequency and very low frequency.

think critically: unlike sound waves, electromagnetic waves can travel in empty space. What evidence supports this statement

you can hear things through your ears that sound wave.