optical lenses

The optical lens is an optically homogeneous transparent body with a …….. index

refraction ….. different from that of the surrounding medium and bound by two surfaces, at least one of which is not a plane

Thin lens is when the

thickness is much smaller than the curvature radii of both surfaces

Thick lens is when

The thickness is not negligible relative to the curvature radii of the surface

The lens is converging when

it increases the convergence of the incident light beam

The lens is diverging when

it increases the divergence of the incident light beam

Focus is the point on the principal optical axis

to which the refracted rays converge when the incident rays are parallel to the optical axis

Focal length of a lens is

the distance between the optical centre and the focal point

Spherical aberration happens when

The rays distant from the axis are refracted more than the central rays, the image of a point is a blurred spot

Chromatic aberration happens when

are focal length is different for rays of different color and the image

Distortion is when

The magnification varies with the distance from the optical axis

When you have astigmatism

At different distances from the lens, the image of a point can be a line , an ellipse, or a circle

Coma is when

magnification varies with the angle between the incident rays and the optical axis

Eye lens is a

transparent elastic double convex body behind the pupil

Adaption is

adjustment of the eye to the level of light

Accommodation is

process of increasing the optical power of the eye lens to focus on objects nearer to the eye

angular resolution limit

the smallest angle of sight between two objects points which are imaged as separate

Myopia is when

images are focused in front of the retina

Hyperopia is when

the images are focused behind the retina

Astigmatism is when

the image on retina is distorted and blurred

If a planar object is not imaged onto a plane , because it is impossible to focus the entire object at one time that is called

field curvature

Rods are ………… senstive ,concentrated at the ………….

less; center

The image on the retina is

diminished,real, inversed

A 60D optical power of the eye means that you are able to focus

distant objects

A 74D optical power of the eye means that you are able to focus

nearby objects

Cones are…….. sensitive, concentrated at the

less ; centre ( fovea )