CLT Photobiology & Light Science 2 — Questions and Answers
Question 1: What is irradiance in the context of light therapy?
- Power per unit area (mW/cm²) (Correct answer)
- Total energy of a treatment session
- The wavelength of light emitted
- The duration of light exposure
Correct answer: Power per unit area (mW/cm²)
Irradiance, measured in milliwatts per square centimeter (mW/cm²), describes the power of light delivered to a surface area at any given moment.
Question 2: What phenomenon occurs when light passes from air into tissue and changes direction?
- Refraction (Correct answer)
- Diffraction
- Polarization
- Coherence
Correct answer: Refraction
Refraction occurs when light changes speed and bends at the boundary between two media with different refractive indices, such as air and skin.
Question 3: Which wavelength range penetrates the deepest into human tissue?
- Near-infrared (700–1100 nm) (Correct answer)
- Ultraviolet (200–400 nm)
- Blue light (400–500 nm)
- Green light (500–565 nm)
Correct answer: Near-infrared (700–1100 nm)
Near-infrared wavelengths (700–1100 nm) penetrate the deepest into tissue because they are least scattered and absorbed by superficial chromophores.
Question 4: What is a chromophore in photobiology?
- A molecule that absorbs specific wavelengths of light (Correct answer)
- A device that measures light output
- A lens that focuses light onto tissue
- A photon unit of measurement
Correct answer: A molecule that absorbs specific wavelengths of light
A chromophore is a molecule capable of absorbing specific wavelengths of light, triggering photochemical or photobiological reactions.
Question 5: The Beer-Lambert Law is used in light therapy to describe which relationship?
- How light absorption increases with chromophore concentration and path length (Correct answer)
- How irradiance decreases with treatment distance
- How fluence correlates with tissue temperature
- How wavelength determines chromophore activation
Correct answer: How light absorption increases with chromophore concentration and path length
The Beer-Lambert Law states that light absorption is proportional to the concentration of the absorbing substance and the path length through which light travels.
Question 6: Which of the following best describes photobiomodulation (PBM)?
- Use of non-ionizing light to stimulate or inhibit cellular functions without generating heat (Correct answer)
- Application of high-intensity lasers to thermally ablate tissue
- Ultraviolet exposure to induce vitamin D synthesis
- Broad-spectrum light used to treat seasonal affective disorder
Correct answer: Use of non-ionizing light to stimulate or inhibit cellular functions without generating heat
Photobiomodulation uses low-level non-ionizing light to modulate cellular processes through photochemical rather than thermal mechanisms.
CLT Photobiology & Light Science 2
What is irradiance in the context of light therapy?