Video Transcript
Which of the following statements
best describes the greenhouse effect? (A) Atmospheric gases trapping
cosmic rays from space and warming the oceans. (B) Atmospheric gases being
destroyed by UV radiation from the Sun. (C) Atmospheric gases reflecting
the heat from the Sun back out into space. (D) Atmospheric gases in the
atmosphere trapping water vapor and lowering sea levels. (E) Atmospheric gases trapping heat
and warming the planet’s surface.
Now, let’s remove the answer
choices from the screen to learn more about this topic.
The Sun is the most important
source of energy for life on Earth. The surface of the Sun is very hot
at about 5000 degrees Celsius. Because the Sun is so hot, it emits
radiation that can travel through space. The main types of radiation emitted
by the Sun are infrared, visible light, and ultraviolet. Infrared radiation has a long
wavelength. Ultraviolet radiation, also known
as UV, has a short wavelength.
When the radiation from the Sun
reaches the Earth, it has to pass through the atmosphere before it reaches the
surface of the Earth. The shorter-wavelength radiation,
such as the visible light and ultraviolet, can pass through the atmosphere. Most of the longer-wavelength
infrared radiation is absorbed by certain gases in our atmosphere. The surface of the Earth absorbs
the shorter-wavelength radiation and warms up. When this happens, the Earth
radiates energy as infrared radiation. Some of this infrared radiation
passes back into space.
Certain gases in the atmosphere,
such as carbon dioxide, water vapor, and methane, absorb some of this infrared
radiation. This causes the lower atmosphere
layer to heat up. The gases that cause this
atmospheric heating are known as greenhouse gases. The heating of the lower atmosphere
by these gases is known as the greenhouse effect. Scientists are concerned that the
warming of the lower atmosphere will cause excessive heating of Earth’s surface.
Now we know more about the
greenhouse effect, let us look at our answer choices to decide which one best
describes the greenhouse effect. The greenhouse effect happens when
heat trapped by gases in the atmosphere warms the Earth. The best description of this
process is found in answer choice (E). Atmospheric gases trapping heat and
warming the planet’s surface is the correct answer.