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7 marksPhysics of the Ear and Eye

CAPE Physics Unit 1 · 2006 · Paper 2 · Question 6(b)(ii)

Using lenses with a power of 2.5 D in her glasses, a woman can comfortably read a book held 25 cm from her eyes.

Determine the woman's near point (i.e. the distance from her eyes where she can see objects clearly without her glasses).

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Other parts of this question

  1. 6(a)(i)Explain the following terms as they relate to the human eye: Accommodation.[3 marks]
  2. 6(a)(ii)Explain the following terms as they relate to the human eye: Astigmatism.[3 marks]
  3. 6(a)(iii)Explain the following terms as they relate to the human eye: Cataract.[3 marks]
  4. 6(b)(i)With the aid of a diagram explain the eye defect from which she suffers.[7 marks]
  5. 6(c)(i)What intensity of sound is considered to be the threshold of human hearing?[10 marks]
  6. 6(c)(ii)Why is the response of the human ear said to be logarithmic?[10 marks]
  7. 6(c)(iii)Explain why sound intensity levels are often measured using a decibel (dB) scale.[10 marks]
  8. 6(c)(iv)A noisy motorbike emits noise with an intensity of 6 x 10⁻² W m⁻². What is the intensity level in dB?[10 marks]
  9. 6(c)(v)Over what range of frequencies would a normal human ear be able to hear a sound with an intensity level of 20 dB?[10 marks]

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