COT EXAM QUESTIONS AND ANSWERS WITH COMPLETE SOLUTION The range of wavelengths in the visible spectrum is? - 400 - 800 nanometers Immediately on either side of the visible spectrum are the invisible light segments of? - Infrared & ultraviolet Which color has the longest wavelength? - Red Geometric optics includes? - The effects of media on the path of light When light bounces back from an object, this is known as? - Reflection In reflection, the light rays that hit the object or interface between media with different indices of refractio n are called? - Incident rays In optics, a medium (or media, plural) is: - An object that reflects light When light passes through a transparent medium, it may travel straight through (transmission) or its path may be altered. This altering or bending pr operty of a medium is known as? - Refraction The ray of light that enters a transparent medium is termed? - Incident ray If light passes through a lens and the rays are spread apart on exiting, this is known as? - Divergence If light passes through a le ns and the rays are spread toward each other on exiting, this is known as? - Convergence A comparison of the speed of light in air to the speed of light through substance is? - IR (Snell's Law) The denser the substance, the more slowly light passes throu gh it and the what? - The higher the IR The IR of crown glass is? - 1.50 Light traveling through a prism will be bent toward the prisms what? - Base The image of an object viewed through a prism Is what? - Virtual and shifted toward the apex A 1.00 diopter prism bends light? - 1 cm at a distance of 1m from the prism A 2.00 diopter prism displaces an object 1cm at a distance of what? - 05 m The displacement of an object 5cm at a distance of 1m would require prism of what? - 5.0 diopters At a distance of 2m, a 12 diopter prism would displace an object how far? - 24cm A spherical lens refracts light? - Equally in every direction A 1.00 diopter spherical lens focuses light at? - 1meter The point at which a lens forms an image (whether real or virtual is the what? - focal point True of false, regarding the optical center of a lens it always coincides with the geometric center of the lens? - False The focal length of a lens is what? - The distance between the lens and the focal point Because the focal point of a minus lens is virtual, the focal length of a minus lens is what? - Likewise virtual What is the formula for finding the focal length? - P = 1/F What is the focal length of a 5 diopter lens? - 0.2 m A lens has a focal length of 33cm what is its dioptic power? - 3 diopters Name 3 characteristics of a cylindrical lens? - 1. They are used to correct astigmatism 2. They have power in one axis, but no power in the axis 90 degrees away 3. They focus light in a line The direction of the line of light as focused by a plus power cylindrical lens is what? - Aligned with the axis Light passing through a cylindrical lens is focused in 2 lines perpendicular to each other & separated by an area known as what? - Sturm's inte rval The light rays in the Sturm's interval are projected in the shape of a what? - cone Within the Conoid of Sturm the area where the image would be most clearly focused is? - The circle of lease confusion An optical cross is a means of what? - Indicat ing the dioptic power of a lens The ocular media consists of? - The tear film, cornea, humors & lens Which ocular structure has the highest refractive power? - Cornea The primary goal of the eye's components is to what? - Focus incoming light onto the r etina Images pass through the optic nerve & thence to the what? - Chiasm, optic tract, lateral geniculate body, & optical cortex All of the following are true regarding the accommodative reflex except: It is stimulated by a blurred image, It is not a tru e reflex, It is required for viewing distant objects or it includes convergence, miois & focusing - It is required for viewing distant objects When the ciliary muscle relaxes what happens? - The lens is pulled thinner The main reason one's accommodation ability decreases with age is due to what? - Hardening of the crystalline lens With accommodation fully relaxed what is the pt's point of clearest vision? - the far point the power of a myopic eye itself is what? - plus the retinoscope provides information on the pt's refractive status by doing what? - reflecting light off the pts' retina the streak retinoscope permits what? - neutralization of individual ocular meridians all of the following are components of the strea k retinoscope except which one? light & power sources condensing lens & mirror rotating lens system focusing sleeve - rotating lens system raising or lowering the focus sleeve of a streak retinoscope does what? - changes the vergence of the light leaving the instrument the plane mirror effect is used in streak retinoscopy because? - this projects parallel light rays into the eye if a streak retinoscope is habitually placed flat on the table what will happen? - the filament may bend causing a distorted st reak a working lens is required in retinoscopy in order to? - simulate working at infinity standard retinoscopy working distance is - 66cm if you use a retinoscopy working distance this is closer than the standard your working lens will need to be what? - more plus power than standard which of the following can be determined with the most accuracy using a streak retinoscope? sphere power, sphere axis, cylinder power or cylinder axis? - cylinder axis the magnitude of a refractive error can often be eval uated by noting all of these streak qualities except: brightness, width, speed or height? - height in streak retinoscopy the intercept is what? - the part of the streak that falls on the pt's iris if you sweep the retinocope streak across the pt's pupil & the reflex travels in the same direction as the intercept this is known as what? - with motion most retinoscopists prefer to neutralize with motion because why? - against motion can be difficult to evaluate one can convert any situation to with motion by adding what? - enough minus sphere one matches the retinoscope streak to the axis of the refractive error by doing what? - rotating the sleeve until there is an unbroken line as the measurement approaches neutrality, the reflex will become what? - brighter, wider & faster` at the point of neutrality the reflex will? - seem to blink on & off all of the following regarding use of the streak retinoscope are true except? 1. keep the room lights low, 2. keep both of your eyes open, 3. measure the pt's rig ht eye with your right eye or 4. when using your right eye, hold the retinoscope in your left hand. - when using your right eye hold the retinoscope in your left hand. to help stabilize the retinoscope & maintain alignment do what? - rest it against your brow or spectacle frame if your pt is not dilated for retinoscopy, instruct him to look at what? - a target on the distance chart if your pt is fully dilated for retinoscopy, you should do what? - concentrate on the central portion of the reflex in stre ak retinoscopy if the streak is vertical you should what? - sweep the streak left to right in your initial retinoscopy evaluation (using the proper lens) you note that that pt has "against" motion in every meridian, this indicates what? - myopia
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