3a.3 - The Eye and Total Internal Reflection Flashcards

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1
Q

What is the cornea? (2)

A
  • A transparent ‘window’ with a convex shape

- And a high refractive index

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2
Q

What does the cornea do?

A

Most of the eye’s focusing

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3
Q

What is the iris?

A

Made up of muscles that control the size of the pupil

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4
Q

What does the iris do?

A

Controls the intensity of light entering the eye

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5
Q

What is the lens? (2)

A
  • Connected ciliary muscles by suspensory ligaments

- When the ciliary muscles contract, tension is released

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6
Q

What does the lens do?

A

Changes shape to focus the light from objects at varying distances

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7
Q

What is the retina?

A

Covered in light-sensitive cells

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8
Q

What does the retina do?

A

The cells detect light and send signals to the brain to be interpreted

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9
Q

Describe what is meant by the near point of the eye?

A

The closest distance the eye can focus on

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10
Q

Is the image on a camera real or virtual?

A

Real

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11
Q

What is the near point of the eye? (2)

A
  • The closest point the eye can see

- Approximately 25cm

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12
Q

Describe how the eye focuses on objects at various distances (3)

A
  • The ciliary muscles contract or relax
  • To change the shape of the lens
  • To focus at different distances on the retina
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13
Q

What eye condition can be caused by the cornea being too powerful?

A

Short sightedness

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14
Q

What type of lens can be used to correct long sightedness?

A

Converging

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15
Q

Suggest two ways shortsightedness can be corrected

A

Put a diverging lens in front of the eye

Remove corneal tissue using a laser

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16
Q

What two conditions are needed for total internal reflection?

A
  • The wave must be travelling from a dense substance to a less dense substance
  • The angle of incidence must be greater than the critical angle
17
Q

How do you calculate refractive index?

A

Refractive index= 1
——-
Sin C

18
Q

What is an endoscope?

A

An endoscope is a thin tube containing optical fibres that allow surgeons to examine inside the body

19
Q

What are the two bundles of optic fibres contained in an endoscope?

A
  • Carry light to the area of interest

- Carry an image back

20
Q

What is an advantage of endoscopes?

A

Can perform many operations by cutting tiny holes