Question 1: Define absorption in the context of black body radiation.

Answer: Absorption is the process by which a material takes in electromagnetic radiation, converting it into internal energy, thereby preventing it from being transmitted or reflected.

Question 2: Explain how the absorption properties of a material affect its temperature when exposed to radiation.

Answer: Materials that absorb more radiation tend to increase in temperature more quickly because they convert more of the incident radiation into internal energy, leading to greater heating.

Question 3: What is the difference between absorption and reflection in the context of electromagnetic waves?

Answer: Absorption involves taking in energy from the wave, converting it into internal energy within the material, whereas reflection involves bouncing the wave off the surface without energy transfer into the material.

Question 1: A black panel absorbs 85% of incident radiation of power 200 W. Calculate the power absorbed by the panel.

Answer: Power absorbed = 0.85 × 200 W = 170 W

Question 2: If a material has an absorption efficiency of 60% and is exposed to radiation of power 150 W, what is the actual power absorbed?

Answer: Power absorbed = 0.60 × 150 W = 90 W

Question 1: Describe a simple experiment to compare the absorption of different coloured materials when exposed to the same source of infrared radiation.

Answer: Set up several samples of different colours (e.g., black, white, red, blue) in identical containers exposed to the same infrared radiation source. Measure their temperature increase over a fixed period using a thermometer. Variables include material colour (independent), temperature change (dependent), and radiation intensity (control). Safety precautions involve ensuring the source is properly shielded and students wear protective equipment to avoid burns.

Question 2: Identify three variables that should be controlled in an experiment measuring absorption of radiation by materials.

Answer: Radiation intensity, exposure time, and material thickness.

Question 1: A sample of aluminium foil is exposed to a radiation source. The measured temperature increase is less than that of a black cloth under the same conditions. Explain what this indicates about aluminium’s absorption properties.

Answer: It indicates that aluminium foil has a low absorption efficiency for the radiation, reflecting or transmitting most of the incident energy rather than absorbing it.

Question 1: Explain how absorption properties are utilised in designing solar thermal collectors.

Answer: Solar thermal collectors use materials with high absorption efficiency, such as blackened surfaces, to maximise the absorption of solar radiation, converting it into heat for water or air heating systems.

Question 2: Describe one safety consideration when conducting experiments involving radiation sources to study absorption.

Answer: Ensure radiation sources are properly shielded and students wear protective equipment to prevent burns or exposure to harmful radiation.