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Pulse oximeters and ECGs are used to monitor the blood oxygen levels and heart activity of a patient - Edexcel - GCSE Physics - Question 6 - 2015 - Paper 1
Question 6
Pulse oximeters and ECGs are used to monitor the blood oxygen levels and heart activity of a patient. (a) Pulse oximeters are often attached to a finger. They use b... show full transcript
Worked Solution & Example Answer:Pulse oximeters and ECGs are used to monitor the blood oxygen levels and heart activity of a patient - Edexcel - GCSE Physics - Question 6 - 2015 - Paper 1
Step 1
Which of these is correct for red light and infrared radiation?
Answer
The correct option is C: red light has a shorter wavelength than infrared. This is due to the electromagnetic spectrum, where red light (with wavelengths approximately 620-750 nm) indeed has shorter wavelengths compared to infrared radiation (which ranges from about 750 nm to 1 mm).
Step 2
A student investigates absorption of light.
Answer
To analyze the data, we observe how the intensity of light at the detector changes with varying thicknesses of absorbers:
- At a thickness of 0.0 mm, the intensity is 0.23 mW/cm².
- At 7.5 mm, the intensity decreases to 0.16 mW/cm².
- At 15.0 mm, the intensity is 0.11 mW/cm².
- At 22.5 mm, the intensity drops further to 0.08 mW/cm².
- Finally, at 30.0 mm, the intensity is 0.06 mW/cm².
This trend indicates that as the thickness of the absorber increases, the intensity of light detected decreases, demonstrating the absorption property of the materials.