Endoscopy

Question 1

State the effect of increasing the refractive index of cladding of an optical fibre

Answer 1

smaller difference between the core index and cladding index makes critical angle larger
therefore increases the chance of light escaping

Question 2

State the effect of bending the fibre into a tighter curve would have on a optical fibre

Answer 2

makes internal angle of incidence at core-cladding interface
more likely to be less than the critical angle
therefore increases the chance of light escaping

Question 3

application of coherent bundle

Answer 3

coherent bundles of fibres transmit images

Question 4

application of non-coherent bundle

Answer 4

non-coherent bundles transmit (or conduct) light

to inside the human body for illumination

Question 5

Advantages of a bundle consisting of fibres of very small diameter over a bundle consisting of larger fibres

Answer 5

high resolution
very flexible bundle
finer fibres allow bending round tighter curves without escape of light

Question 6

Reasons why a glass cladding is used around the central core of each fibre in a coherent bundle

Answer 6

so that scratches on the outer surface do not allow light to escape and so that close contact between adjacent fibres

Question 7

Explain how a digital camera can store the image produced by the endoscope

Answer 7

charge coupled device / CCD
Capacitor stores charge as light falls on it
Charge depends on light intensity

Question 8

Explain what is meant by crosstalk and how it limits the usefulness of the endoscope

Answer 8

Ray leaving one fibre and entering adjacent fibre

Reduces resolution / image will be blurred / less clear / limits angle through which fibre may be bent