This set is currently a work in progress. It will cover A Beka Book Physics Chapter 20: "The Refraction of Light" (pages 292-308).

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• ### optical density

term for a material's resistance to the transmission of light waves

### wavelength, speed

When light enters a new medium, _____ and ___ change.

### decrease

The wavelength of light entering an optically denser medium must _____.

### increase

The wavelength of light entering a medium of lower optical density must ______.

### refraction

term for the bending of light rays at the boundary between two media differing in optical density

### transmitted

If two adjoining media have the same optical density, light is fully _____.

### absorbed, reflected

If a new medium is nontransparent, light is partly ____ and partly _____.

### transmitted, reflected

If both media are transparent, but have different optical densities, some light is ____ and some is ____.

### refractive index

term for the index that relates the speed of light in a vacuum to the speed of light in a particular medium

### refractometer

term an instrument that measures refractive index

### angle of incidence

term for the angle between an incoming ray and the normal to the boundary

### angle of refraction

term for the angle between a refracted ray and the normal to the boundary

### n1 sin θ1 = n2 sin θ2

the first law of refraction

### Snell's law

another term for the simple relationship expressed by the first law of refraction

### principle of reversibility

principle that states that the path of a light ray subjected to reflection or refraction is traced in reverse by any ray coming along the path in the opposite reaction

### mirage

A ____ of water is due to the refraction of sunlight as it passes through hot, expanding air at ground level.

### critical angle

When the angle of incidence reaches the ____ ___, the angle of refraction becomes 90 degrees.

### total internal reflection

term for reflection as a result of an angle of incidence greater than the critical angle

### convex

term for a bulging surface with the same curvature as the surface of a sphere

### concave

term for a caved-in surface witht he same curvature ast he surface of a sphere

### planar

term to describe a flat surface

### convergig lenses

term for lenses that redirect parallel rayst oward a point of convergence

### double convex lenses

the most important converging lenses

### diverging lenses

term for lenses that spread parallel rays apart

### double concave lenses

the most important diverging lenses

### positive

Convergenging lenses have a _____ (positive, negative) focal length.

### negative

Diverging lenses have a ____ (positive, negative) focal length.

### normal

term for the perpendicular to a plane at the point of tangency

### principal axis

term for the axis which is perpendicular to the lens plane

### principal focal point

term for the point of convergence on the opposite side of the lens, to which rays are directed

### optical center

term for the center of the lens

### focal length

term for the distance from the optical center to the principal focal point

### secondary focal point

another term for the focal length

### optical plane

term for a plane perpendicular to the principal axis at the optical center

### parallel ray

term for a ray that travels parallel to the principal axis, and then refracts through the mirror to the principal focal point

### central ray

term for a ray that pases through the optical center of a lens without deviation on the far side

### focal ray

term for a ray that aproaches the lens through the focal point

### real image

term for actual light rays intersecting after refraction

### virtual image

term for light rays extending from a lens in order to intersect

### 1/f = (n-1) (1/r1 - 1/r2)

the lensmaker equation

### 1/f = 1/do + 1/di

the thin lens equation

### myopia and hyperopia

two defects of vision that can be corrected by wearing eyeglasses or contact lenses

### myopia

term for nearsightedness

### hyperopia

term for farsightedness

### P = 1/f

the equation for the power of a lens

### diopter

the unit for the power of a lens

Example: