A physics exhibit to show the effect of the aerosol in the atmosphere on electromagnetic wave propagation

In this paper it is explained the construction and utility of a didactic exhibit about the effect of aerosol in atmosphere on electromagnetic wave propagation. The exhibit is composed by a lamp simulating the Sun, a Plexiglas case (the atmosphere), white or black panels (surface albedo), a combustion chamber to supply aerosol inside the case and other equipments. There are temperature and relative humidity of air sensors and 5 light sensors to measure direct and scattered light. It is possible to measure the cooling effect of aerosol inside the case and the increasing in scattered light.

💡 Research Summary

The paper presents the design, construction, and educational use of a tabletop physics exhibit that demonstrates how atmospheric aerosols affect electromagnetic wave propagation, specifically visible and near‑infrared light. The core of the exhibit is a 30 cm cubic Plexiglas chamber that serves as a miniature atmosphere. A 1500–2700 K “spot” lamp positioned at the top simulates solar illumination, while two interchangeable surface panels at the bottom represent high‑albedo (white/ice) and low‑albedo (black/sea) conditions. The panels can be raised, lowered, and rotated by a small DC motor, gearbox, and Arduino‑controlled mechanism, allowing students to switch albedo states during an experiment.

A simple combustion chamber beneath the Plexiglas box burns small pieces of paper to generate aerosol particles. The smoke is drawn through copper tubing that is continuously cooled by circulating water/ice, preventing the aerosol from heating the chamber interior. A separate water‑vapor generator can increase relative humidity inside the chamber.

Five SFH206K photodiodes monitor light intensity: one on the top measures reflected light, one on the bottom measures direct light, and two on the side walls capture light scattered at 90°. A UV/IR cut filter isolates the visible band for one sensor. The photodiodes are housed in black paper tubes to limit their field of view. Temperature is recorded with an LM35 analog sensor, and relative humidity with a digital RHT01 sensor. All sensors are wired to an Arduino UNO (ATmega328); analog signals pass through a 6‑channel multiplexer, while the humidity sensor uses a digital pin. The Arduino streams data via serial USB to a PC, where a simple script logs the values and Gnuplot updates real‑time plots every two seconds.

The experimental protocol begins with the lamp on and the chamber warmed for about two hours without added humidity. Baseline data are collected for both albedo settings. Then the paper is ignited, aerosol is introduced, and the cooling system operates. Measurements are repeated with the aerosol present. Results show a clear increase in the side‑wall and top‑photodiode readings (enhanced scattering) and a decrease in the bottom‑photodiode reading (reduced direct transmission) when aerosol is present. The LM35 records a temperature drop of roughly 2 °C, while the RHT01 indicates a modest rise in relative humidity. The white‑albedo configuration consistently yields higher overall light levels than the black‑albedo case, but aerosol‑induced scattering is evident in both.

The authors argue that the exhibit effectively visualizes the dual role of aerosols: they scatter incoming solar radiation, increasing diffuse illumination, while simultaneously reducing the amount of direct solar energy reaching the surface, leading to a net cooling effect. This mirrors real‑world climate dynamics where aerosols can offset greenhouse‑gas warming.

Critical assessment highlights several strengths: low cost, modularity, hands‑on control of albedo, and integration of multiple sensors for a comprehensive data set. The use of a cooled combustion source is inventive, reducing thermal artifacts. However, the study lacks quantitative characterization of aerosol size distribution and concentration, which limits the ability to compare results with atmospheric radiative transfer models. The lamp’s spectrum deviates from true solar radiation, especially in the UV, and the photodiodes are not fully shielded from ambient light, potentially introducing systematic errors. The Arduino’s ADC reference voltage (0.54 V) reduces dynamic range, and the data‑logging approach is simplistic, lacking timestamps, redundancy, or long‑term storage.

Future improvements could include: (1) adding a particle counter or optical particle sizer to measure aerosol properties; (2) employing a solar‑simulating lamp with a more accurate spectrum; (3) using calibrated broadband radiometers or spectrometers for multi‑wavelength analysis; (4) enhancing light‑shielding and using collimated optics to improve measurement fidelity; (5) implementing robust data acquisition software with timestamped CSV files and cloud backup; and (6) expanding the experimental matrix to explore varying humidity, aerosol types, and albedo combinations.

In conclusion, the exhibit provides an accessible, visually engaging platform for teaching atmospheric physics and climate concepts at the secondary‑school or museum level. With modest upgrades, it could also serve as a low‑cost research test‑bed for exploring aerosol radiative effects, bridging the gap between classroom demonstration and scientific investigation.