BOSTES HSC Physics 2015 Question 31

Question: 
This question is asked in the context of geophysics. Students are expected to explain the impact of “remote sensing applications” on society. Three examples should be provided in the answer. 

Marking Guidelines:

Criteria	Marks
• Assess the impact of remote sensing applications on society. • Support the answer using three specific examples.	6

(Source: https://www.boardofstudies.nsw.edu.au/hsc_exams/2015/guides/2015-hsc-mg-physics.pdf)

Sample answer: 
1. Satellites have improved weather forecasts by capturing images that track weather events such as a hurricane or typhoon. This provides early warnings that help to save lives and protect properties.
2. Using infrared sensors to monitor vegetation helps to improve crop yields and plan for production shortages. This may allow food to be redistributed in areas where there are possible shortages.
3. Using magnetic sensors for mineral exploration such as detecting iron ore deposits. This can be done promptly such that societies have access to minerals efficiently.

Comments:

To achieve six marks in this question, students are expected to make informed judgments about the impact of the remote sensing applications on society and support their answers using three specific applications. However, there are more than hundreds of specific applications of remote sensing. For instance, we could classify applications of remote sensing in terms of electromagnetic waves. Importantly, according to Sabins (1997), “[r]emote sensing is the science of acquiring, processing, and interpreting images and related data, acquired from aircraft and satellites, that record the interaction between matter and electromagnetic energy (p. 1).” In other words, we can focus on common applications in which the basic principle involves electromagnetic waves. Below are three examples of remote sensing applications that are closely related to geophysics:

1. Visible light waves: This refers to satellite images that record visible light waves from the earth’s surface. For example, Google Earth allows everyone to view satellite images, maps, or terrains for purposes such as navigation. However, satellite images can also be used for monitoring of volcanic eruptions and island formations (natural or artificial).

2. Infrared waves: The radiations recorded in the infrared satellite images can be a measure of temperature. It is also useful to use infrared light sensors to detect forest hot spots which could be caused by lightning or arson. Alternatively, infrared sensors can be used to monitor the temperature of earth’s surface to have a deeper understanding of global warming issues.

3. Radio waves: The altitudes of mountains, lands, and seas can be monitored by using radio waves. That is, radio waves are transmitted by satellites and the altitude of earth’s surface can be determined by measuring the time it takes the waves to reflect back to the radar. These altitude measurements can be useful for construction purposes such as building bridges or tunnels.

Applications of remote sensing include a wide range of fields such as agriculture, archaeology, cartography, hydrology, meteorology, and oceanography. However, students’ answers should be closely related to geophysics which is the context of the question. Importantly, the three examples should show significant impacts of remote sensing on society.

Feynman insights?: 

Remote sensing commonly involves the use of various instruments and electromagnetic waves to see earth’s physical processes. It should be insightful to explain this principle of remote sensing by using the following words of Feynman, “[t]he electromagnetic field can carry waves; some of these waves are light, others are used in radio broadcasts, but the general name is electromagnetic waves. These oscillatory waves can have various frequencies. The only thing that is really different from one wave to another is the frequency of oscillation. If we shake a charge back and forth more and more rapidly, and look at the effects, we get a whole series of different kinds of effects, which are all unified by specifying but one number, the number of oscillations per second. The usual ‘pickup’ that we get from electric currents in the circuits in the walls of a building have a frequency of about one hundred cycles per second. If we increase the frequency to 500 or 1000 kilocycles (1 kilocycle = 1000 cycles) per second, we are ‘on the air,’ for this is the frequency range which is used for radio broadcasts. (Of course, it has nothing to do with the air! We can have radio broadcasts without any air.) If we again increase the frequency, we come into the range that is used for FM and TV. Going still further, we use certain short waves, for example for radar. Still higher, and we do not need an instrument to ‘see’ the stuff, we can see it with the human eye. In the range of frequency from 5 × 10¹⁴ to 10¹⁵ cycles per second our eyes would see the oscillation of the charged comb if we could shake it that fast, as red, blue, or violet light, depending on the frequency. Frequencies below this range are called infrared, and above it, ultraviolet. The fact that we can see in a particular frequency range makes that part of the electromagnetic spectrum no more impressive than the other parts from a physicist’s standpoint, but from a human standpoint, of course, it is more interesting (Feynman et al., 1963, section 2-2 Physics before 1920).” Alternatively, a broader definition of remote sensing may include magnetic fields and gravitational fields in addition to electromagnetic fields.

Essentially, physics teachers should explain that remote sensing may involve electromagnetic waves such as visible light waves, infrared waves, or radio waves. Furthermore, all these waves, which contain a great amount of information, are the same kind of waves that differ in the wavelength or frequency. Interestingly, during a BBC interview, Feynman (1994) explains that “[t]he radio waves are just the same kind of waves, only much longer waves. Then there’s the radar from the airplane which is looking at the ground to figure out where it is, which is coming through this room too, plus X-rays, cosmic rays, all these other things which are exactly the same kind of waves, just shorter and faster, or longer and slower - it’s all the same thing. So this big field, this big area of irregular motions, this electric field, this vibration contains a tremendous information (p. 132).” However, Feynman may be perceived as sloppy when he uses terms such as longer waves instead of longer wavelengths.

References: 

1. Feynman, R. P. (1994). No Ordinary Genius: The Illustrated Richard Feynman. New York: W. W. Norton & Company. 
2. Feynman, R. P., Leighton, R. B., & Sands, M. (1963). The Feynman Lectures on Physics, Vol I: Mainly mechanics, radiation, and heat. Reading, MA: Addison-Wesley.
3. Sabins, F. F. (1997). Remote Sensing - Principles and Interpretation (3rd ed.). New York: W.H. Freeman.