Which statement describes the relationship between frequency and absorption?

• A. Absorption decreases with frequency
• B. Absorption increases with frequency
• C. Absorption is independent of frequency
• D. Absorption varies randomly with frequency

Answer: (B)

The main idea here is how a material’s ability to absorb energy from a wave changes as the wave’s frequency changes. Higher-frequency photons carry more energy, making it easier to drive electronic or vibrational transitions that cause absorption. As a result, the material tends to absorb more as frequency increases, which is why the statement that absorption increases with frequency is the best fit.

In contrast, saying absorption decreases with frequency, or that it’s independent, doesn’t match the common trend of stronger interaction at higher energies. And describing the absorption as varying randomly ignores the systematic ways that absorption usually depends on frequency due to available transitions and interaction strength.