Temperature and Heat Exchange

Question 1

How is the zone of peak emission determined?

Answer 1

Substance’s temperature which is given by Wein’s Law.

Question 2

What does Wein’s law state? What is its principle?

Answer 2

• The wavelength of a radiation body’s peak emissions is inversely proportional to its absolute temperature.
• Hotter a body, shorter the wavelength of that body’s peak emissions.

Question 3

What is the typical range of a wavelength of a substance?

Answer 3

Between 0.2 to 5.6 micromillimeters.

Question 4

What is the range of wavelength of the solar energy emitted by the sun? What is the wavelength of the maximum radiation output?

Answer 4

• 0.5 to 5 micromillimeters.

- 0.48 micromillimeters

Question 5

What is the percentage value and wavelength range of UV value?

Answer 5

• 7 to 9%

- 0.001 to 0.39 micromillimeters

Question 6

What is the percentage value and wavelength range of visible light?

Answer 6

• 45 to 47%

- 0.39 to 0.78 micromillimeters

Question 7

What is the percentage value and wavelength range of near-infrared/infrared?

Answer 7

• 46% (combined)
• 0.78 to 4 micromillimeters (near infrared)
• 4 to 100 micromillimeters (infrared)

Question 8

Define sky radiation

Answer 8

Radiation that reaches the earth after having been scattered by clouds and aerosols in the atmosphere.

Question 9

Define global/total solar radiation

Answer 9

Total solar radiation received by the Earth is the sum of sky radiation and direct radiation, which is called global solar radiation.

Question 10

How does the distance between the sun and the earth affect the amount of solar energy received by the Earth.

Answer 10

• Greater amount of solar energy received at all latitude increases when the Earth is closer to the sun.
• Less solar energy received at all latitudes when the Earth is further away from the sun

Question 11

What affects the distance between the sun and the Earth?

Answer 11

What orbital cycle the Earth is currently in as the Earth’s orbit moves between highly elliptical and nearly circular in a cycle that lasts roughly 100,000 years.

Question 12

In the Southern Hemisphere, what is it called when the Earth is furthest away from the sun? What is the distance and when does it occur?

Answer 12

• Aphelion
• 152 million km
• Occurs in July (winter)

Question 13

In the Southern Hemisphere, what is it called when the Earth is closest to the sun? What is the distance and when does it occur?

Answer 13

• Perihelion
• 147 million km
• Occurs in December (summer)

Question 14

How does the altitude of the sun affect the amount of solar energy received by the Earth?

Answer 14

• Earth is on an axial tilt of 23.5º, thus the latitude where solar input is perpendicular shifts north and south.
• Basically meaning that only one latitude on the Earth’s rotating surface can receive radiation at 90º, while all other latitudes receive it obliquely.
• Where the oblique angle is acute, the sun’s energy must travel a greater distance to reach the Earth’s surface.

Question 15

When is the vertical sun at its most northern latitude?

Answer 15

June

Question 16

When is the vertical sun at its most southern latitude?

Answer 16

December

Question 17

What months receive greater solar radiation in the Northern Hemisphere?

Answer 17

Between the end of March and September

Question 18

What months receive greater solar radiation in the Southern Hemisphere

Answer 18

Between the end of September and March

Question 19

When does nil insolation occur at the poles?

Answer 19

During the polar winter months

Question 20

When does constant insolation take place at the poles?

Answer 20

During the polar summer months

Question 21

What is the maximum angular input at the poles? When does it occur?

Answer 21

20º in the middle of the summer polar period.

Question 22

How does the length of day affect how much solar energy the Earth receives?

Answer 22

A greater length of day will result in greater radiation output as there is a greater amount of time for the sun to output solar radiation.

Question 23

Where in the world is it that the number of hours of daylight equals dark hours?

Answer 23

Equatorial regions at 12 hours each.

Question 24

Is daylight shorter than night in summer and vice versa in winter?

Answer 24

No, daylight is longer in summer.

Question 25

When do the hours of daylight and dark equal each other all over the world occur? Specifically, what dates do these events occur?

Answer 25

• When the perpendicular sun is exactly over the geographical equator.
• Twice a year, on or about 22 March and 22 September. Known as the equinoxes