Question

What conclusion can be made based on the temperature of soil when the light hits the soil at 0°, 45°, and 90° angles in Section 2 of the experiment? Did your results support your hypothesis? Why or why not?

Answer 1

First, clarify angle convention: I’m assuming the angles are measured from the soil surface so that 0° = light skimming the surface (very oblique), 45° = intermediate, and 90° = light straight down (perpendicular/direct). If your experiment used a different convention (angles from the normal), swap the labels accordingly.

Conclusion
- Soil temperature increased as the light became more perpendicular: lowest at 0°, higher at 45°, and highest at 90°.
- This pattern is expected because a beam that strikes the surface more directly delivers more energy per unit area.

Did the results support the hypothesis?
- If your hypothesis predicted that soil would be warmest when light is most direct (90°) and coolest when most oblique (0°), then yes — the results support the hypothesis.
- If your hypothesis predicted a different order, then the results do not support it.

Why (physics and experiment reasons)
- Physics: irradiance on a surface scales with the cosine of the incidence angle (cosine law). As the angle becomes more oblique, the same amount of light is spread over a larger area, so energy per unit area and heating drop. Also, oblique rays can be reflected more and pass through slightly more air (small effect in lab).
- Experimental factors that confirm or could disturb the pattern: lamp distance, uneven soil moisture, sensor placement, time allowed for temperatures to equilibrate, ambient air currents, and measurement error. If one of these was uncontrolled it could weaken agreement with the hypothesis.

If your data deviated from the expected trend, check for those sources of error (ensure consistent lamp distance, repeat trials, allow steady-state temperature, use identical soil samples).