Correcting Vision Flashcards
What is the far point? What is it for normal people?
The furthest distance that the eye can focus on comfortably.
Infinity
What is the near point? Where is it for adults?
The closest distance that the eye can focus on.
Approximatley 25cm
As the eye focuses on closer objects, its power [ ] - the lens changes shape and the [ ] decreases. But the distance between the lens and the [ ] stays the same.
increases
focal length
image
What is short sight corrected with?
Diverging lenses
What can’t short sighted people focus on?
Distant objects - their far point is closer than infinity
What is short sight caused by? Why are things out of focus?
The eyeball being too long or by the cornea and the lens system being too powerful - this means that the lens can’t produce a focused image on the retina where it is supposed to.
Can you draw the diagram for correcting short sight with a diverging lens?
Do it!
What is long sight corrected with?
Converging lenses
What can’t long sighted people focus on?
Near objects - their near point is further away than normal
What is long sight caused by?
The eyeball being too short or by the cornea and the lens system being too weak
Where are near objects brought to focus for long sighted people?
Behind the retina
Can you draw the diagram for correcting long sight with a converging lens?
Do it!`
What is a laser?
A narrow, intense beam of light. All the light waves that come from a laser have the same wavelength
What can lasers cut through?
Body tissue
What can lasers do to protect against infection in a patient?
Cauterise small blood vessels - reduces blood loss
