3.1 (P2) Lenses And Eye Flashcards
What are the two types of lenses?
Converging (convex)
Diverging (concave)
What do converging lenses do?
Causes parallel light rays to converge to a point
What does a diverging lens do?
Causes parallel light rays to diverge from a point (spread out)
Difference between image and object?
You start with the object
You create the image
What lens is used in camera/eye?
Converging/convex
What is the outcome of the image in camera/eye?
Real
Inverted
Diminished
Does the image end up on the same or opposite side of the object in camera/eye?
Opposite side
What lens is used in a projector?
Converging/convex
Where does the object have to be for projector?
Closer than twice the focal point
Further than the focal point
What is the outcome of the image in projector?
Real
Inverted
Enlarged
Does the image end up on the same or opposite side of the object in projector?
Opposite side
What lens is used in a magnifying glass?
Converging/convex
Where does the object have to be for a magnifying glass?
Closer than the focal point
What is the outcome of the image in a magnifying glass?
Virtual
Upright
Enlarged
Does the image end up on the same or opposite side of the object in a magnifying glass?
Same side
Where does the object have to be for a diverging lens?
Further than the focal point
What is the outcome of the image in a diverging lens?
Virtual
Upright
Diminished
Does the image end up on the same or opposite side of the object in a diverging lens?
Same side
What is a real image?
Where light rays converge
What is a virtual image?
Where virtual light rays converge or where light rays appear to converge
In the eye what is the function of the blindspot?
Where the retina is not sensitive to light
In the eye what is the function of the ciliary muscle?
Changes the thickness of the eye lens
In the eye what is the function of the cornea?
Transparent layer that protects the eye
Helps focus the light on to the retina
In the eye what is the function of the iris?
Ring of muscle that controls the amount of light entering
In the eye what is the function of the lens?
Focuses the light on to the retina
In the eye what is the function of the optic nerve?
Carries nerve impulses from the retina to the brain
In the eye what is the function of the pupil?
Hole formed by the iris allowing light rays through
In the eye what is the function of the retina?
Light sensitive cells receive light rays and convert them into neural signals
What is the power of a lens?
It’s ability to bend light
The greater the power…
The greater the refraction of light
What is power of a lens measured in?
Dioptre - singular
Diopters - plural
What is the power of a converging lens?
Positive
What is the power of a diverging lens?
Negative
Where does the object have to be for camera/eye?
More than 2F (twice focal point) away
What is focal length measured in?
Meters
What lens corrects short sightedness (myopia)? Why?
Diverging
The light rays previously converged before the retina
What lens corrects long sightedness (hyperopia)?
Converging
The light rays previously converged beyond the retina
What is focal length determined by?
Refractive index of the material of a lens
The curvature of two surfaces of the lens
For a given focal length:
The greater the refractive index…
Meaning…
The flatter the lens
The lens can be manufactured thinner
What is the eyes range of vision?
25cm to infinity
Depends on each person
What are the two equivalents in a camera and the eye?
Retina and CCD’s
