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# Seasons and Sun - PowerPoint PPT Presentation

Seasons and Sun. Sun Angle and Solar Heating Investigation 3, Part 3. Lesson Objective: I can explain how beam spreading affects the temperature of the Earth in different locations. The tilt of Earth’s axis produces changes in day length over the course of a year. Review.

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### Seasons and Sun

Sun Angle and Solar Heating

Investigation 3, Part 3

Lesson Objective:I can explain how beam spreading affects the temperature of the Earth in different locations.

The tilt of Earth’s axis produces changes in day length over the course of a year

Review

Earth rotates on its axis to produce day and night

Questions- over the course of a year.

• What kind of weather do you generally associate with summer?

• What is it about summer that makes it hotter?

• What happens to produce more heat?

Answer? over the course of a year

• Longer days means

more time for the Sun’s energy to be absorbed by the:

• Land

• Water

• Atmosphere

• Maybe that’s why it’s hotter???

But could there be more to this story?

Circle the brightest spot on the graph paper over the course of a year

Light Model

Observe the spot of light where the beam hits the floor

To represent a beam of light from the Sun

Form of energy over the course of a year

The circles show the area that the energy beam covered at two different times.

Light

Both are sources of light energy.

Beam Spreading over the course of a year

• Discuss the demonstration/lab in your group.

• Work together to answer the questions 1-3 on Beam spreading.

Observations

Spot gets bigger as the angle between the beam of light and floor gets smaller.

• Amount of light energy in the beam stays the same.

• Both spots deliver the same amount of energy to the paper.

Open your ISN. angle.Title the next page: How Beam Spreading Affects the Temperature of the Earth

Energy travels from the Sun to Earth as radiation, or solar energy. Heat is transferred to the Earth by radiation.

Solar Angle- angle.

Angle at which light strikes a surface (add definition to ISN)

Light rays from directly overhead have a high solar angle.

Low solar angle rays hit the Earth’s surface at about 15˚.

Think of it like this: angle.

• If you spread jelly evenly on a cracker and the same amount of jelly on a piece of bread, the jelly on the cracker will be thicker than the jelly on the piece of bread. You will get more jelly with each bite of cracker than with the piece of bread.

When fewer rays hit an area, the energy density is low. Not as much energy is transferred to that part of the Earth.

Energy Density-

Number of rays hitting a given area is the energy density. (add definition to ISN and draw a picture of this example)

When lots of rays hit an area, the energy density is high.

Notice rays are equally spaced in both beams,

but because of solar angle,

there are three times as many rays when it is from a high solar angle.

Beam Spreading as much energy is transferred to that part of the Earth.

• The way a light beam covers a larger area when it hits a surface at an angle

• Even though, the same amount of energy is hitting the surface, it is more dense, more intense when coming from directly overhead. The higher the angle, the more intense solar energy.

Penny Question as much energy is transferred to that part of the Earth.

• Answer the fourth question on your Beam Spreading sheet.

90˚

30˚

Penny Question Answer as much energy is transferred to that part of the Earth.

Amount of energy hitting it varies with the solar angle

Surface area of a penny does not change

90˚

30˚

The greater the angle, the greater the energy it will receive.

Solar Angle and Earth as much energy is transferred to that part of the Earth.

Earth is round = the angle at which light hits it is different from place to place

Sunlight

Earth viewed as many flat surfaces

Light strikes surfaces that are at different angles.

Solar Angle on Earth as much energy is transferred to that part of the Earth.

30˚

Angle between the incoming rays of light and the surface of the land is the solar angle.

45˚

Solar angle = 60˚

Solar angle = 90˚

Sunlight on Earth’s Surface as much energy is transferred to that part of the Earth.

Light energy from the Sun is distributed over a larger area when it hits Earth’s surface at an angle.

Beam spreads more and more the farther north or south your go.

Does the same thing if you move east and west

Afternoon Sun as much energy is transferred to that part of the Earth.

Energy is most intense

High solar angleBeam spreading is small, the angle is 90 degrees at noon, so that is the most intense time of day

Morning and Evening Sun as much energy is transferred to that part of the Earth.

Energy is least intense

Low solar angleBeam spreading is large

The Results as much energy is transferred to that part of the Earth.

Solar energy is most intense during the middle of the day in the tropics.

Energy is least intense in the morning, evening and extreme north and south regions.

Solar Energy- as much energy is transferred to that part of the Earth.Take NOTES in ISN!

• Almost all of the energy coming to Earth is solar energy.

• Light absorbed by the land, water, and air is converted to heat.

• Heat is the form of energy that makes things happen in the atmosphere.

Summary as much energy is transferred to that part of the Earth.

• Areas of the planet where solar radiation shines direction down on Earth are subjected to more intense energy than areas that experience beam spreading. The great the amount of energy absorbed, the hotter the area becomes. This is why the hottest part of Earth is in the region of the tropics (near the equator).

Why is summer as much energy is transferred to that part of the Earth. hotter than winter?

• Because the Earth’s axis is tilted, the Northern Hemisphere received more intense solar energy in the summer months, making summer HOTTER!

• During the winter months, sunlight strikes the Northern Hemisphere at a low solar angle, resulting in less heating from solar radiation, making it COOLER!

Beam Spreading as much energy is transferred to that part of the Earth.

• Answer question 5 by copying the information below.

• The solar angle affects how much energy is received in an area. A large solar angle means more energy per area on Earth’s surface. Smaller solar angles result in beam spreading, delivering less energy per area to Earth’s surface.

If you are finished, read a book. as much energy is transferred to that part of the Earth.