Week 4 & 5 - BVS 120.1: Prisms and Deviation

Flashcards covering key vocabulary, concepts, and formulas related to thick and thin prisms, including deviation, critical angle, total internal reflection, minimum deviation, and perpendicular incidence from BVS 120.1 lectures.

Prism

A lens block with plane surfaces that are NOT parallel.

Apex (Prism)

The point where the two inclined surfaces of a prism meet; it determines the amount of deviation.

Base (Prism)

The surface that is directly opposite the apex of a prism.

Lateral Deviation

Occurs when the angle of incidence (i1) results in an identical angle of refraction from the second surface (i2'), leading to no angular deviation as incident and exiting rays are parallel.

Angular Deviation (Prism)

Occurs when the sides of a lens block incline towards each other, meaning the sides are no longer parallel, creating a prism.

Angle of Deviation (d)

The angle created by the intersection of the initial ray (i1) and the final exiting ray (i2') after passing through a prism. It is also the angle between the un-deviated ray and the final refracted ray.

Refracting Angle (A)

Also known as the apical or principal angle, it is the sum of both internal angles (i1' + i2) of a prism.

Upright Prism (Rarer Medium)

When surrounded by a rarer medium, light bends towards the base of the upright prism, and the image is displaced towards the apex, forming a virtual image.

Plane Waves (Prism)

Waves that pass through a prism without changing vergence.

External Angles (Prism)

The incident angle (i1) at the first surface and the exiting angle (i2') at the second surface of a prism.

Internal Angles (Prism)

The refracted angle (i1') at the first surface and the incident angle (i2) at the second surface of a prism.

Snell's Law (Prism - 1st Surface)

n sin i1 = n' sin i1', used to calculate refraction at the first surface of a prism.

Snell's Law (Prism - 2nd Surface)

n sin i2 = n' sin i2', used to calculate refraction at the second surface of a prism.

Prism Deviation Equation

d = i1 + i2' - A, an equation used to calculate the total angle of deviation for a prism.

Principle of Reversibility

States that if the path of light through a prism is reversed, the angle of deviation will remain unchanged, though the direction of light changes.

Positive Angle of Deviation (d)

Occurs when the refractive index of the prism is greater than the surrounding medium (n prism > n surrounding), causing light to deviate towards the base.

Negative Angle of Deviation (d)

Occurs when the refractive index of the prism is less than the surrounding medium (n prism < n surrounding), causing light to deviate towards the apex.

Maximum Deviation (Thick Prism)

Occurs in a thick prism when either the incident angle (i1) or the exiting angle (i2') is 90 degrees (grazing incidence or exit).

Critical Angle (ic)

The angle of incidence in the denser medium that results in an angle of refraction of 90 degrees in the rarer medium. Formula: sin ic = n'/n (rare/dense).

Total Internal Reflection (TIR)

Occurs when the angle of incidence in the denser medium exceeds the critical angle, causing all light to reflect back into the denser medium.

Law of Reflection (TIR)

When total internal reflection occurs at a surface, the angle of incidence equals the angle of reflection (i2 = i2').

Minimum Deviation (dmin)

A condition where the two external angles (i1 and i2') are numerically equal, and the internal ray crossing through the prism is perpendicular to the bisector of the apical angle. Formula: dmin = 2i1 - A.

Perpendicular Incidence (Prism)

Occurs when light is incident perpendicular to the normal (i1 = 0, i1' = 0) at the first surface, meaning there is no refraction at that surface, only bending.

Prism Diopters (P)

A unit used to measure how much a prism bends or shifts light from its original path. Formula: P/100 = y/x, where y is linear deviation and x is distance.

Thick Prism

A prism classified by an apical angle (A) greater than 10 degrees.

Thin Prism

A prism classified by an apical angle (A) less than 10 degrees.

Thin Prism Approximation

A simplified formula for deviation in thin prisms: d = (n-1)A. It is only accurate for prisms with apical angles less than 10 degrees, and deviation does not depend on the angle of incidence.

Angle of Deviation to Prism Diopters Conversion

P = 100 (tan d), a formula to convert the angle of deviation (d in degrees) into prism diopters (P).