Wave properties Vocab: Crest - Highest part of the wave (yellow) Trough - Lowest part of the wave, opposite of the crest (purple) Amplitude (A, power) - maximum displacement, how much energy a wave can carry (orange) Wavelength (represented by lamba, λ) - distance of one entire oscillation, from crest to crest, from trough to trough, or from equilibrium to equilibrium (green) Equilibrium position - the horizontal line in the middle of the wave (black) Transverse wave - a transverse wave is a wave whose oscillations are perpendicular to the direction of the wave's advance. Longitudinal wave - a longitudinal is a wave in which the vibration of the medium is parallel to the direction the wave travels and displacement of the medium is in the same direction of the wave propagation. Frequency - frequency refers to the number of waves that pass a fixed point in unit time. It also describes the number of cycles or vibrations undergone during one unit of time by a body in periodic motion. (formula for frequency) - f(frequency) = 1 / t(period) Eyeball anatomy Vocab: Cornea - the transparent part of the eye that covers the iris and the pupil and allows light to enter the inside. (yellow) Pupil - the round opening in the center of the iris. The pupil changes in size to let light into the eye. It gets smaller in bright light and larger as the amount of light decreases. (purple) Lens - a nearly transparent biconvex structure suspended from the iris of the eye, with the sole function to focus light rays onto the retina. (orange) Iris - the colored at the front of the eye that contains the pupil in the center. The iris helps control the size of the pupil to let more or less light into the eye. (green) Ciliary body - this is found behind the iris and includes the ring-shaped muscle that changes the shape of the lens when the eye focuses. It also makes the clear fluid that fills the space between the cornea and the iris. (black) Sclera - the white layer of the eye that covers most of the outside of the eyeball. (gray) Choroid - a thin layer of tissue that is part of the middle layer of the wall of the eye, between the sclera and the retina. The choroid is filled with blood vessels that bring oxygen and nutrients to the eye. (red) Retina - a thin layer of tissue that lines the back of the eye on the inside. It is located near the optic nerve. The purpose of the retina is to receive light that the lens has focused, convert the light into neural signals, and send these signals on to the brain for visual recognition. (blue) Optic nerve - a bundle of more than 1 million nerve fibers that carry visual messages. You have one connecting the back of each eye (your retina) to your brain. Damage to an optic nerve can cause vision loss. The type of vision loss and how severe it is depends on where the damage occurs. (pink) Rods and cones - Rods are responsible for vision at low light levels (scotopic vision). They do not mediate color vision, and have a low spatial acuity. Cones are active at higher light levels (photopic vision), are capable of color vision and are r-o9esponsible for high spatial acuity. Light and color Vocab Refraction - the bending of a wave as it passes from one medium to another ROYGBIV - red, orange, yellow, green, blue, indigo, violet Information - The wave model of light helps us to explain how light is composed of different colors - White light from sources like the sun is made up of all the colors of the rainbow → ROYGBIV (red, orange, yellow, green, blue, indigo, violet) - Each color has a slightly different wavelength and frequency - lowest frequency = red - highest frequency = violet - Different wavelengths slow down different amounts and so they are refracted different amounts when they pass from one medium to another, so when the white light is passed through a prism, the light is separated into the different colors - A rainbow is also caused by refraction (as well as reflection) → the refraction as light enters and exits the water droplets causes the colors to be seperated just like when light passes through the prism - Objects appear to be the colors they are because they reflect the color that they are, and absorb others / for example - red objects absorbs orange yellow green blue indigo and violet, and reflects red, white objects reflect all of them, and black objects absorbs all of them - The primary colors of light are red, green, and blue. These are the primary colors of light because you only need these colors to produce white. Medium of light Vocab Transparent - materials that allow light to pass through them. These materials transmit all light rays that strike them; hence objects can be seen clearly through them. Examples - air, water, glass Translucent - materials that allow some light to pass through them. The light is scattered in many directions as it passes through these objects; hence objects may usually seem blurry. Examples - frosted glass, wax paper Opaque - an object that doesn't allow light to pass through it. Hence, objects cannot be seen through them. Most objects are opaque and include things made of wood, stone, and metal. Models of light Vocab Model - a way of representing something that we can't see so that we can understand it better and make predictions Wave model - A good model for understanding why light is made up of different colors and how it fits into the whole electromagnetic spectrum - Explains transfer of energy - Explains color spectrum Particle model - Light is made up of photons - Photons are like packets of light waves - Light can occasionally travel as a particle Ray model - Views light as a straight line with an arrow on it (a ray) which travels in a given direction - A good model for analyzing how light acts when it encounters mirrors, lenses, and other surfaces - Light normally travels in a straight line Reflection of light Vocab Normal - a line drawn at right angles to a solid barrier such as a mirror Incident ray - the incoming light ray to the barrier Reflected ray - the light ray that bounces off the barrier Angle of incidence - the angle between the incident ray and the normal. It is often labeled with i. Angle of reflection - the angle between the reflected ray and the normal. It is often labeled with an r. The law of reflection states that the angle of incidence is equal to the angle of reflection. Plane mirror - flat, smooth mirror Concave - a mirror that curves inward. If parallel light rays are shone on a concave mirror, they reflect so that the light rays converge to a focal point. Convex - a mirror that curves outward. If parallel light rays are shone on a convex mirror, they reflect so that the light rays diverge. (if you extend the reflected rays backward behind the mirror, they converge to a virtual focal point. Images formed by mirrors Plane mirror - characteristics → the image is upright → the image is the same size as the object → it is the same distance behind the mirror as the object is in the front → it appears to be reversed left - right (although it is actually front - back) Concave mirror - characteristics → if the image is far away from the mirror, the image is inverted and smaller → as the image approaches the focal point, the image stays inverted but image starts to get larger → if the image is closer to the mirror than the focal point, then the image is upright and larger (make-up mirrors) Convex mirror - characteristics → the image is upright and smaller → as the object approaches the mirror, the image gets larger, but it is still smaller than the object → they have a wide field of view - we can see objects over a larger area than we can with a plane mirror. (convenience stores, parking garages, passenger side car mirror) Extra Converge - Convergence is the physical joining together of light rays. Light rays tend to come together at a point (called point of convergence or focal point) from different directions Diverge - A lens that causes parallel light rays to spread out – hence diverge – away from the optical axis once exiting the lens. The lens surfaces may be plano-concave, double concave or concave-convex. The edge of a diverging lens is always thicker than the center. Whenever an image is upright, it is a virtual image since it cannot be formed on a screen and can only be seen by looking at the mirror. So plane mirrors and convex mirrors always form virtual images. Whenever an image is inverted, it is a real image and can be formed on a screen. So a concave mirror forms a real image when the object is far from the mirror and a virtual image when the object is close to the mirror. Refraction of lenses Convex lenses converge, whereas convex mirrors diverge. Concave lenses diverge , whereas convex mirrors converge. why can sound travel in space: For sound to occur sound waves must travel through air, however in space, there is no air, meaning that it is impossible for sound to travel in space.
