Optics 2.0

Part 1: Written Test

  a. Teams will be given a minimum of 20 minutes to complete a written test consisting of multiple choice,

true-false, completion, or calculation questions/problems.

  b. Unless otherwise requested, answers must be in metric units with appropriate significant figures.

  c. The test will consist of at least 5 questions from each of the following areas:

i. Reflection and refraction: Specular & diffuse reflection, Law of Reflection, index of refraction,

Snell’s law, critical angle, and prisms (deviation & dispersion)

Reflection: occurs when light bounces off a surface.

Refraction: the bending of light when it passes through one medium to another. (Ex. air to water)

Specular reflection: a way of reflection that resembles a mirror. all rays bounce off in the same direction.

Diffuse reflection: a way of reflection where light is scattered in a number of angles instead of just a singular one.

Law of Reflection: the angle of incidence is equal to the angle of reflection.

Index of Refraction: used to determine the angle at which light refracts at a boundary, defined by the ratio of the speed of light in a vacuum to the speed of light in the medium.

Snell’s Law: calculates refraction, n1sin(theta)1=n2sin(theta)2

Critical Angle: the angle of incidence at which the angle of refraction is 90 degrees.

Deviation of Prisms: occurs when ray of light is incident on the prism and deviates from its original path; Δ = i1 + i2 − A

Dispersion of Prisms: A dispersive prism separates light into its spectral components (colors of the rainbow);  different wavelengths (colors) of light are deflected by the prism at different angles; white light passing through the prism is separated into its component colors: red, orange, yellow, green, blue, and violet.

ii. Mirrors & lenses: Convex, concave, and plain mirrors and lenses; ray tracing; focal length; real,

virtual, erect, and inverted objects and images; magnification

Convex lens: A lens that curves outward, thicker in the middle than at the edges. It converges light rays to a focal point, forming real images if the object is beyond the focal length or virtual images if the object is within the focal length.

Concave lens: A lens that curves inward, thinner in the middle than at the edges. It diverges light rays, spreading them out. Concave lenses always produce virtual, upright, and smaller images.

Plane mirrors and lenses: A flat mirror that reflects light without distorting or bending it, producing virtual, upright, and same-size images; Flat piece of glass that doesn’t focus or alter the path of light in the way a convex or concave lens does.

Ray tracing: A method for determining the path of light as it travels through lenses or reflects off mirrors.

Focal Length: The distance from the center of a lens or mirror to its focal point, where parallel light rays converge (in a convex lens or mirror) or appear to diverge (in a concave lens or mirror).

Real objects: Physical objects that emit or reflect light rays, forming real or virtual images when viewed through lenses or mirrors.

Virtual objects: Points where light rays appear to originate, though they don't physically exist at that location. Often produced in multi-lens or multi-mirror systems.

Erect objects: Objects oriented in their natural, upright position when viewed through lenses or mirrors.

Inverted objects: Objects oriented upside-down compared to their original position when viewed through lenses or mirrors.

Real images: Images formed by actual convergence of light rays at a point, producing an image that can be projected onto a screen. Real images are typically inverted relative to the object.

Virtual images:  Images formed by the apparent (but not actual) divergence of light rays from a point. They cannot be projected onto a screen and are always erect, as in the case of images seen in a plane mirror.

Erect images: Images oriented in the same upright position as the object. Virtual images are always erect; real images can be erect or inverted depending on the lens or mirror setup.

Inverted images: Images oriented upside-down relative to the object. Real images are typically inverted when formed by convex lenses or concave mirrors.

iii. Color theory: Additive & subtractive color theory; primary & secondary colors; absorption &

reflection

Additive color theory: A color theory describing how light colors combine. In additive color mixing, the primary colors are red, green, and blue (RGB). When combined, they produce white light. This theory applies to light sources, such as screens.

Subtractive color theory:  A color theory describing how pigments or filters remove (subtract) certain wavelengths of light, producing color by absorption and reflection. The primary colors in subtractive theory are cyan, magenta, and yellow (CMY), and when combined, they produce black. This theory applies to printed materials and paints.

Primary colors: 

Additive Primary Colors: red, green, blue. Mixing these colors in varying intensities can produce the full spectrum of visible colors in light.

Subtractive Primary Colors: cyan, magenta, yellow. These colors combine in various ways to produce other colors in pigments or inks.

Secondary colors:

Additive Secondary Colors: cyan, magenta, yellow. Created by mixing two additive primary colors.

Subtractive Secondary Colors: red, green, blue. Created by mixing two subtractive primary colors.

Absorption: The process in which a material takes in light energy rather than reflecting or transmitting it. Absorbed light is often converted into heat. This is fundamental in subtractive color mixing, where pigments absorb certain wavelengths and reflect others.

Reflection: The bouncing of light waves off a surface. Smooth surfaces, like mirrors, reflect light at consistent angles, producing clear images, while rough surfaces scatter light in multiple directions, diffusing it.

iv. Structure and function of the human eye

Sclera: helps maintain the eyeball’s shape and supports it

Iris: the colored part of the eye that controls the size of the pupil;adjusts to regulate the amount of light entering the eye

Cornea: clear, dome–shaped front layer that covers the iris and pupil; helps focus light into the eye by bending it towards the lens

Pupil: The black circular opening in the center of the iris that allows light to enter the eye; expands or contracts to adjust the size of the pupil based on light levels

Lens: located behind the pupil; further focuses light onto the retina; changes shape to adjust focus for near or distant objects (accommodation)

Ciliary Body and Muscle: surrounds the lens and controls its shape for focusing; muscle contracts or relaxes to make the lens thicker or thinner, adjusting focus.

Conjunctiva: thin membrane covering the sclera and inner eyelids; helps keep the eye moist and protect it from dust/microbes

Retina: thin layer of tissue at the back of the eye where light-sensitive cells (rods and cones) detect light and convert it into electrical signals sent to the brain

Optic Nerve: nerve that transmits visual information from the retina to the brain, allowing us to interpret what you see

Macula: central part of the retina responsible for high-resolution, color vision, especially important for tasks like reading and recognizing faces

Retinal Blood Vessels: provide essential nutrients and oxygen to the retina, helping to keep the retina in place.

Rods: enable us to see in low-light conditions; lack color

Cones: responsible for detecting color and fine detail.

Ray Diagrams and Mirrors:

If object is between F and C, the image forms beyond C and it is magnified in size.

If object is between P and F, the image will not form or it will be a virtual image.

The closer you bring the object to the mirror, the bigger the image.

If ray is shot at F, the reflected ray will be parallel to the principal axis

If ray is shot at C, the reflected ray will go through C as well.

If ray is shot at P or any other point on the line ≠ F or C, use the law of reflection (angle of incidence=angle of reflection)