2.7: Alternative Text Descriptions for Investigation 2

Figure 2.1.2 Different types of Heat Transfers

An educational diagram illustrating four methods of heat transfer: conduction, convection, radiation, and advection. A fire is at the center bottom of the image.

• Convection is shown as upward motion of warm air from the fire toward a pair of hands held above it, indicating heat transfer through the movement of heated air.

• Radiation is demonstrated by wavy lines traveling directly from the fire to another pair of hands held at a distance in front of the fire, representing direct heat transfer through electromagnetic waves.

• Conduction is depicted by a person holding a metal rod in their hand, with the opposite end placed in or near the fire. This shows heat traveling through the solid rod from the hot end to the hand.

• Advection is represented by particles or dots moving horizontally away from the heated air, symbolizing horizontal heat transfer through bulk fluid motion.

The diagram is designed to clarify how thermal energy moves in different ways depending on the medium and mechanism.

Figure 2.2.1 The Electromagnetic Spectrum

A labeled diagram of the electromagnetic spectrum focusing on the range of human-visible light. The visible spectrum is positioned between ultraviolet and infrared regions. The top section marks visible wavelengths in nanometers, ranging from 400 to 750 nm. Below it, a horizontal scale shows corresponding electromagnetic categories—such as ultraviolet radiation, infrared radiation, microwaves, and radio waves—with their associated wavelength values (from 1 femtometer to 10 megameters) and frequency values (from 10²⁴ Hz to 10⁴ Hz). Key divisions like cosmic radiation, gamma rays, X-rays, radar, and alternating currents are labeled accordingly.

This diagram illustrates the full electromagnetic spectrum, highlighting the portion of light that is visible to the human eye, which spans wavelengths from approximately 400 to 750 nanometers. The spectrum is organized from left to right by increasing wavelength and decreasing frequency.

To the left of visible light are shorter wavelengths and higher frequencies, representing high-energy radiation. This includes cosmic radiation (starting near 1 femtometer), gamma rays, and various types of X-rays (hard, medium, soft). These radiations are mostly invisible and hazardous to biological tissue.

Immediately before the visible spectrum is ultraviolet radiation, divided into UV-C, UV-B, and UV-A types. The visible spectrum is situated in the middle of the chart and ranges from 400 to 750 nanometers. This is the only portion of electromagnetic radiation detectable by the human eye.

To the right of visible light, the wavelengths grow longer and frequencies drop. This includes infrared radiation, followed by terahertz radiation and microwaves, which are commonly used in communication and cooking appliances.

Beyond these lie radio waves, organized into bands such as ultra high frequency (UHF), very high frequency (VHF), and others including shortwave, medium wave, and longwave. At the far right are low-frequency alternating currents with extremely long wavelengths, used in electrical power systems.

The diagram also includes logarithmic scales along the bottom:

• Wavelength, measured in meters, ranges from 10⁻¹⁵ meters to 10⁷ meters.

• Frequency, measured in hertz (Hz), ranges from 10²³ Hz to 10⁻³ Hz.

This spectrum provides a comparative view of how electromagnetic radiation types are distributed by wavelength and frequency, with the visible portion emphasized for reference.

Figure 2.4.1: Absorption Spectrum

A scientific diagram titled "Atmospheric Transmission" showing how much electromagnetic radiation is absorbed or scattered by Earth's atmosphere at different wavelengths. The horizontal axis is labeled with wavelength in micrometers and nanometers, ranging logarithmically from approximately 10⁻³ micrometers (gamma rays) to 10⁶ micrometers (radio waves). Major sections along the wavelength axis are labeled as gamma rays, X-rays, ultraviolet, visible, infrared, and radio waves. The vertical axis represents the percentage of atmospheric absorption and/or scattering, from 0% to 100%.

On the top panel, two curves are plotted: one representing the atmosphere’s transmission in the visible spectrum and another in the infrared spectrum. The diagram highlights transmission “windows” where the atmosphere allows more radiation to pass through—especially in parts of the visible and radio wave regions—while also showing regions with low transmission due to absorption by gases like water vapor, ozone, and carbon dioxide.

Labeled regions of absorption include water vapor bands in the infrared and microwave ranges, ozone absorption in the ultraviolet, and a general blocking of gamma rays and X-rays. This visualization illustrates how the composition of the Earth's atmosphere affects which parts of the electromagnetic spectrum reach the surface.

Figure 2.5.1: Lines of Latitude

A globe showing the Atlantic Ocean, parts of North and South America on the left, and parts of Europe and Africa on the right. The diagram highlights latitude lines running horizontally from the South Pole to the North Pole in 15-degree increments. The labeled lines are: 45°S, 30°S, 15°S, 0° (Equator), 15°N, 30°N, 45°N, 60°N, and 75°N. The equator is prominently labeled in bold text. The map illustrates how these latitude lines wrap around the Earth, and their values increase the further away you get from the equator. 

Figure 2.5.4: Sunlight When Sun is Over Equator

Diagram of Earth showing how sunlight hits different parts of the planet. The circle represents Earth, with "NP" (North Pole) at the top, "SP" (South Pole) at the bottom, and the Equator marked across the center. Two orange sunlight beams approach from the right. One beam hits the Equator directly, showing concentrated energy in a small area. The other beam hits the upper part of Earth near the North Pole at an angle, spreading the same amount of sunlight over a larger area. This demonstrates why equatorial regions are warmer and polar regions colder.

Figure 2.5.5: Global Average Air Temperatures

World map showing average yearly temperatures using colors. The equator region is colored red and dark orange, indicating the hottest temperatures around 20 to 30 degrees Celsius. Temperatures get cooler moving toward the poles, shifting to yellow, green, blue, and purple. The coldest areas near the North and South Poles are pink and white, showing temperatures as low as minus 50 degrees Celsius. A color scale below the map ranges from -50°C to +30°C and is labeled in both Celsius and Fahrenheit. Title reads "Annual Mean Temperature."

Figure 2.5.6: Earth's Orbit

A diagram shows Earth’s orbit around the Sun, illustrating how the tilt of Earth's axis causes seasonal changes. The Sun is at the center with four labeled Earth positions around it, each representing a different season in both hemispheres.

• June 20/21 (top left): Earth's North Pole is tilted toward the Sun. The Northern Hemisphere receives the most direct sunlight, leading to summer there. The Southern Hemisphere receives less sunlight, resulting in winter.

• September 22/23 (bottom left): Earth's axis is not tilted toward or away from the Sun. Both hemispheres receive roughly equal sunlight. This marks the autumn equinox in the Northern Hemisphere and spring equinox in the Southern Hemisphere.

• March 20 (top right): Similar to September, sunlight is evenly distributed between hemispheres. It is the spring equinox in the Northern Hemisphere and autumn equinox in the Southern Hemisphere.

• December 21/22 (bottom right): Earth's South Pole is tilted toward the Sun. The Southern Hemisphere receives the most direct sunlight, experiencing summer, while the Northern Hemisphere gets less sunlight, causing winter.

Each Earth in the diagram shows a consistent tilt in its axis. Seasons in the Northern Hemisphere are labeled in yellow, and corresponding Southern Hemisphere seasons are labeled in lavender. A red arrow shows Earth’s orbital direction around the Sun.

Figure 2.5.7: Conditions in June

Diagram of Earth tilted on its axis, showing how sunlight reaches different latitudes. The Earth is drawn as a circle with a tilt to the right. The North Pole (NP) is at the top, the South Pole (SP) at the bottom, and the Equator is labeled in the center. Two additional latitude lines are shown: 23.5 degrees North (Tropic of Cancer) and 23.5 degrees South (Tropic of Capricorn).

Three horizontal orange bars labeled “Sunlight Beam” enter from the right, representing sunlight:

• The top sunlight beam fully covers the North Pole and the region around 23.5°N, showing that the Arctic is in continuous sunlight—experiencing 24 hours of daylight.

• The middle beam strikes the Equator directly, indicating the most concentrated solar energy in that region.

• The bottom beam misses the South Pole, leaving it in shadow. This shows the Antarctic is in continuous darkness, experiencing 24 hours of night.

This diagram illustrates how Earth's axial tilt affects sunlight distribution during the June solstice, causing one hemisphere to experience continuous daylight while the opposite has continuous darkness.

Figure 2.5.8: Conditions in December

Diagram of Earth tilted on its axis to illustrate sunlight distribution during the December solstice. Earth is shown as a circle tilted to the left. Labels mark the North Pole (NP) at the top, the South Pole (SP) at the bottom, and the Equator across the middle. Two additional latitude lines are labeled: 23.5 degrees North (Tropic of Cancer) and 23.5 degrees South (Tropic of Capricorn).

Three orange horizontal bands labeled “Sunlight Beam” enter from the right, representing incoming solar radiation:

• The top sunlight beam does not reach the North Pole, indicating that the Arctic Circle is in full darkness, with 24 hours of night.

• The middle beam hits the Equator, showing balanced solar exposure at this latitude.

• The bottom beam directly hits the South Pole, demonstrating that the Antarctic Circle is fully illuminated, with 24 hours of daylight.

This diagram visually explains that during the December solstice, the Southern Hemisphere is tilted toward the Sun, resulting in summer and longer days. The Northern Hemisphere is tilted away, experiencing winter and shorter days, including polar night conditions near the Arctic Circle.

Figure 2.6.1: Length of Day vs. Month

Graph showing how day length changes throughout the year at different latitudes in the Northern Hemisphere. The x-axis represents months from January to December. The y-axis represents hours of daylight, ranging from 0 to 24 hours.

Five color-coded curves represent different latitudes:

• Blue curve (70°N): Shows extreme variation. Peaks at 24 hours of daylight during the June solstice and drops to 0 hours during the December solstice. Represents polar day and polar night.

• Green curve (60°N): Peaks around 19 hours in June and drops to about 5 hours in December.

• Red curve (50°N): Peaks near 16.5 hours in June and falls to about 8 hours in December.

• Orange curve (30°N): Shows less variation, with a peak just over 14 hours in June and a low around 10 hours in December.

• Horizontal purple line (Equator): Constant at 12 hours of daylight all year long.

Vertical dashed lines mark four key astronomical events:

• March Equinox and September Equinox show where all curves intersect near 12 hours, indicating equal day and night at all latitudes.

• June Solstice shows maximum daylight in the Northern Hemisphere.

• December Solstice shows minimum daylight in the Northern Hemisphere.

The graph illustrates that the closer a location is to the poles, the more variation it experiences in day length throughout the year. The Equator receives consistent daylight year-round.

Figure 2.6.2: Total Insolation vs. Month

Line graph showing how solar insolation (incoming solar radiation) varies over the months at different latitudes in the Northern Hemisphere. The x-axis represents months from January (J) to December (D). The y-axis measures insolation in watts per square meter (W/m²), ranging from 0 to 600.

There are four color-coded lines representing different latitudes:

• Orange line (90°N, North Pole): Insolation is zero for much of the year, rising sharply in April and peaking around 500 W/m² at the June Solstice, then dropping to zero again by September. This line shows extreme seasonal variation due to polar night and polar day.

• Red line (60°N): Starts low in winter, rises steeply through spring, peaking just under 500 W/m² in June, then gradually declines through fall and winter.

• Green line (30°N): Shows a more moderate curve, peaking just above 450 W/m² in June and dipping to about 250 W/m² in winter.

• Blue line (0°, Equator): Relatively flat line around 400 W/m² throughout the year, indicating minimal seasonal variation in solar radiation at the Equator.

Four vertical dashed lines mark the March Equinox, June Solstice, September Equinox, and December Solstice, indicating key points in Earth's solar calendar.

The graph shows that higher latitudes receive more variable insolation throughout the year, while the Equator receives consistent sunlight. Peaks in insolation occur around the June Solstice for all Northern Hemisphere locations.