Lens Power Calculation and Lens Maker's Equation Quiz

dioptre, denoted as D

plus (+)

air (n)

<p>F = (n' - n) / r</p> Signup and view all the answers

<p>back surface</p> Signup and view all the answers

<p>A positive sign indicates a convex surface, and a negative sign indicates a concave surface.</p> Signup and view all the answers

<p>A thin plus lens adds positive vergence to light rays.</p> Signup and view all the answers

<p>+2.00D</p> Signup and view all the answers

<p>Incident vergence must be zero, i.e. parallel rays.</p> Signup and view all the answers

<p>back vertex power (BVP)</p> Signup and view all the answers

<p>If the radius of curvature is given in centimetres, a correction of 100 is needed, and if it is given in millimetres, a correction of 1000 is needed.</p> Signup and view all the answers

<p>The sum of the powers of the individual surfaces of the lens.</p> Signup and view all the answers

<p>A positive sign for the radius of curvature indicates a convex surface, and a negative sign indicates a concave surface.</p> Signup and view all the answers

<p>The formula is P = (n' - n) * (1/r1 - 1/r2), where P is the nominal power, n' is the refractive index of the medium light is entering, n is the refractive index of the medium light is leaving, r1 is the radius of curvature of the front surface, and r2 is the radius of curvature of the back surface.</p> Signup and view all the answers

<p>The surface power is +2.50D, calculated using the formula P = (n' - n) / r.</p> Signup and view all the answers

<p>The total power is +5.00D, calculated by adding the nominal powers of the two lenses.</p> Signup and view all the answers

<p>The relationship is P = 1/f, where P is the nominal power in dioptres and f is the focal length in metres.</p> Signup and view all the answers

<p>The lens maker's equation is used to calculate the nominal power of a thin lens from its refractive index and radius of curvature.</p> Signup and view all the answers

<p>+4.00D</p> Signup and view all the answers

<p>The secondary focal point (F')</p> Signup and view all the answers

<p>The secondary focal length (f')</p> Signup and view all the answers

<p>To determine the direction of the light rays and the vergence added by the lens</p> Signup and view all the answers

<p>The primary focal point is where rays diverging from a source would have zero vergence when they exit the lens, whereas the secondary focal point is where incident light with zero vergence leaves the lens and then crosses the optical axis</p> Signup and view all the answers

<p>A plus lens, and it means that the light rays will actually cross at that point</p> Signup and view all the answers

<p>A lens adds vergence to incident light, meaning it changes the direction of light rays. This is achieved through the lens's two polished surfaces, which refract light and alter its path.</p> Signup and view all the answers

<p>The nominal power of a lens is inversely proportional to its focal length. A shorter focal length corresponds to a higher nominal power, and vice versa.</p> Signup and view all the answers

<p>The optical axis is an imaginary line passing through the center of a lens, perpendicular to its surface. The primary focal point is the point on the optical axis where parallel light rays converge, while the secondary focal point is the point where diverging light rays appear to diverge from.</p> Signup and view all the answers

<p>A thin lens is a lens whose thickness is negligible compared to its radius of curvature. The nominal power of a thin lens can be calculated by adding the surface powers of its front and back surfaces.</p> Signup and view all the answers

<p>The power of a lens is dependent on the curvature of its surfaces, with a higher power corresponding to a more curved surface. The sign of the power also depends on the direction of the curvature.</p> Signup and view all the answers

<p>A plus lens adds vergence to light, causing it to converge, while a minus lens reduces vergence, causing it to diverge. The sign of the lens power determines whether it is a plus or minus lens.</p> Signup and view all the answers

<p>The primary purpose of spectacle lenses is to protect the eye from mechanical/chemical injury and reduce the intensity of incident light. They achieve this by either increasing or decreasing the vergence of incident light, depending on the type of surface.</p> Signup and view all the answers

<p>A convex surface bulges and increases the vergence of incident light, having plus power, whereas a concave surface is hollow and decreases the vergence of incident light, having minus power.</p> Signup and view all the answers

<p>A surface with a long radius of curvature is flatter and has lower power, while a surface with a short radius of curvature is steeper and has higher power.</p> Signup and view all the answers

<p>A thin lens is used to correct vision by either increasing or decreasing the vergence of incident light, depending on the type of lens and its power.</p> Signup and view all the answers

<p>Vergence refers to the bending of light as it passes through a lens, and the power of a lens determines the amount of vergence it imparts to the incident light.</p> Signup and view all the answers

<p>The optical axis is an imaginary line that passes through the center of the lens, and it is the reference point for measuring the lens' power and focal length.</p> Signup and view all the answers