FREE ABO NOCE Question and Answers
A lens's power is indicated by the word "axis."
False. A lens's axis indicates where the astigmatism power is located, not how much power is present. The sphere represents the necessary lens power, and the cylinder represents the astigmatism correction power.
What's the term of the phenomenon where the eye tends to turn from its natural position?
When binocular seeing is disrupted, an eye alignment problem is known as a phoria. When the eyes are tired and only seldom noticeable, the person is unable to correct for the deviation. A tropia is when the eye never straightens out and is constantly turned in, out, up, or down, in contrast to a phoria. Exophoria is a transitory condition in which the eyes migrate outward. It is typically brought on by eye fatigue, stress, or occupations requiring close vision. Even when both eyes are open and attempting to cooperate, exotropia—an outward turning of the eyes—is more common and apparent. Exophoria is a transitory condition in which the eyes migrate outward. It is typically brought on by eye fatigue, stress, or occupations requiring close vision. Exotropia is another condition in which the eyes move outward, but it is more common and obvious, even when both eyes are open and attempting to function simultaneously.
What controls the quantity of light that reaches the eye?
The iris muscles regulate the amount of light that enters the eye. These muscles regulate the pupil's size, causing it to enlarge (dilate) to let in more light or contract (constrain) to let in less light. The iris widens, enlarging the pupil in low light, and contracts, narrowing the pupil in high light. One-third of the eye's inherent power is produced by the crystalline lens, which is posterior to the iris and primarily composed of proteins. It focuses light into a picture on the retina. High-acuity vision is produced by the fovea, a small, flat point in the middle of the posterior region of the retina.
You can change a lens' focal length by:
Curvature of one surface is altered. Because light waves are refracted at a greater angle with regard to the lens' optical axis, lenses with higher angles of curvature will have shorter focal lengths. The focal length of the lens shortens as the refractive index rises or gets more curved. The focal length won't change if the lens surface is coated, and increasing the diameter of the lens while maintaining the curvature of the surfaces has no effect on the angle of curvature or the way light waves are refracted.
What sort of lens has a surface that is both convex and concave?
One convex and one concave surface make up a meniscus lens. A positive meniscus lens is steeper on the convex side, making it thicker at the center and thinner on the edges, whereas a negative meniscus is thinner at the center than at the edges. Both myopic and hyperopic eyes can have their vision corrected with meniscus lenses. A biconvex lens has two convex surfaces, whereas a biconcave lens has two concave surfaces. One flat surface and one convex surface make up a plano-convex lens.
What word best describes the direction change of light as it moves from one medium to another?
Refraction describes how light slows down and bends as it transitions from air, a medium with a low density, into clear glass or plastic, a media with a high density. The light will bend toward the normal when it travels from air through a denser medium, such a lens, due to the difference in surface velocities between the two media. Diffusion is the term used to describe how light is dispersed when it passes through an uneven surface. When light bounces off a smooth surface, it is said to reflect; the light will reflect at the same angle as when it first reaches the surface. When white light is refracted, dispersion occurs, dividing it into the colors red, orange, yellow, green, blue, and violet.
Meniscus, equiconcave, and flat concave are varieties of
Minus lenses cure for nearsightedness, often known as myopia, a condition in which a person can see things up close but not far away. The narrowest point of the lenses used to remedy this have a front surface that is flatter than their back surfaces and a center that is more curved. Meniscus lenses have two spherically curved surfaces that are concave on one side and convex on the other. A lens is referred to as equiconcave when both of its concave sides have the same focal length. On one side, flat concave lenses have a flat surface, and on the other, they have a spherical surface. Plus lenses come in the equiconvex, flat convex, and meniscus varieties. Meniscus lenses can be plus or minus, although concave describes minus lenses and convex describes plus lenses.