light and optics unit test

Pythagoras

light comes from our eyes

• problem : why can’t we see in the dark?

Euclid

light travels in straight lines

• when shining light onto a flat mirror, the incoming beam and the mirror is equal to the angle between the reflected beam and mirror

Albert A. Michelson

Speed of light = 299 798 ( distance/speed + j —> j/60 = time in mins OR distance/speed = time in secs

Al-Haythem

light bounces off objects and into our eyes

Newton

white light is made of a mixture of different colors

Ole Rome

first person to measure the speed of light in 1676

properties of light

• travels in straight lines

• can be reflected

• can bend

• form of energy

optical device

any device that uses light

reflecting telescope

large concave mirror that is good at gathering light

• other lens directs light to eyepiece

refracting telescope

has 2 lenses with 1 on each end of tube ( larger = objective lens )

• gathers and focuses rays on eyepiece

microscope

magnifies the image of small objects

• uses 2 or more lenses

binoculars

has 2 short refracting telescopes fixed together

how can optical devices affect what we can see

by manipulating light through refraction (bending) or reflection to alter the magnification, clarity, or perspective of an object

light intensity

brightness

luminous

light producer

ray

light travelling from its source in a straight line that represents the path of light

non-luminous

not producing light

transparent

all light is able to get through

regular reflection

• rays hit a smooth surface

• reflected at same angle ( rays parallel )

translucent

some light can go through

diffuse reflection

• uneven surface

• reflected in different angles ( not parallel )

opaque

no light can go through

light travels in straight ____ until it ____ __ ___

lines , strikes a surface

how does opaque objects reflect, absorb, and/or bend light

• Reflect → light bounces off

• Absorb → light energy is taken in (often becomes heat)

• Bend (refract) → doesn’t happen because light can’t pass through

how does translucent objects reflect, absorb, and/or bend light

• Reflect → some light bounces off

• Absorb → some light is taken in

• Transmit + bend + scatter → light passes through, changes direction, and spreads out

how does transparent objects reflect, absorb, and/or bend light

• Reflect → a little light bounces off

• Absorb → a very small amount is taken in

• Refract (bend) → most light passes through and changes direction

reflected of smooth surface

angle of incidence and angle of reflection are equal

• rays are parallel

reflected off a rough surface

reflected angle and angle of incidence arent equal

• rays are not parallel

incandescent light 95&5

uses a thin wire ( filament )

• electricity flows and creates white-hot

phosphorescent light

glow in the dark and stores energy

PHOSPHORESCENCE

ability to emit light

fluorescent light 28&80

• small amount of gas

• mercury vapour ( excite mercury vapor, producing ultraviolet light that causes a phosphor coating to glow. )

Light-emiting diodes ( LED )

a two-terminal semiconductor device that converts electrical energy directly into light via electroluminescence

phosphor

a solid substance that exhibits luminescence, emitting light when exposed to radiation like ultraviolet light or electron beams

bioluminescence

production and emission of light by a living oragnisms

photophore

light producing organ

most important source of light on earth

sun

primary colors

red , green , blue

secondary colors

cyan ( b + g ) , yellow ( g + r ) , magenta ( r + b )

theory of color addition

mixing of primary colors makes many different colors of light

pixel

the unit of measurement for the size and quality of a digital image or display

white light formation

combining all visible colors of the spectrum (red, orange, yellow, green, blue, indigo, and violet) or, more simply, by mixing the primary colors of light: red, green, and blue

cornea

transparent layer forming the front of the eye

iris

circular band of muscle that controls size of pupil

pupil

opening that allows light to enter

lens

focuses light

cililary muscle

pulls on the lens to change shape

retina

filled with photoreceptors at the back of the eye

photoreceptors

specialized neuroepithelial cells in the retina (rods and cones) that convert light into electrical signals for vision

rods

sensitive to LIGHT

cones

detect COLOR

optical nerve

a bundle of over 1 million nerve fibers that transmits visual information from the retina to the brain

blind spot

• the point of entry of the optic nerve on the retina, insensitive to light

• OR

• an area where a person's view is obstructed.

near sighted

cannot see distance objects clearly

• fixed by thinner convex or concave lenses

far sighted

cannot see upclose

• convex lenses

similarity with human eyes and cameras

pupil —> aperature

iris —> diaphragm

eyelid —> shutter

retina —> film

difference in how human eyes and cameras change the focus if light

• Eye: changes lens shape

• Camera: moves lens or internal parts

• Eye: automatic and continuous

• Camera: mechanical or digital adjustment

focus of light in near sightedness

caused by the eye not being able to make lens thin enough to focus light onto retina

• far from retina

focus of light in far sightedness

eye cant make lens fat enough

• behind retina

camera eyes

has cornea, lens, and retina

vertebrate

an animal of a large group distinguished by the possession of a backbone or spinal column, including mammals, birds, reptiles, amphibians, and fishes.

compound eyes

made up of smaller units called OMMATIDIUM

ommatidium

long tube with a lens on outer surface, focusing cone below, and a light sensitive cell

secondary waves

seismic body waves that travel through the Earth's interior after an earthquake, arriving second after primary (P) waves

aftershock

a smaller earthquake following the main shock of a large earthquake

seismograph

an instrument that detects, measures, and records seismic waves caused by earthquakes, explosions, or volcanic activity

richter scale

a scale that seismologists use to measure the amount of ground shaking and energy that is released from earthquakes

fault

fractures in Earth's crust where movement has occurred

difference between fish , birds , and nocturnal eyes

fish : has perfectly round lens so they can see in any direction ( bulges out pupil )

birds : has 5 different cones so they can distinguish more colors and shades

nocturnal : 1) very large pupil to collect lots of light

2) tapedum lucidum - acts like a mirror

3) more rods than cones

plane mirror

A flat reflective surface that produces clear, undistorted reflections.

reflected ray

ray reflected off mirror from incident ray

incident ray

ray coming in

angle of incidence

angle between normal line and incident ray

angle of reflection

angle between normal line and reflected ray

concave mirror

curved inward

• images are closer / larger ( collects light from a large area to bring it to a focal point - between mirror and focal point )

convex mirror

bulge out

• images are smaller and further away ( focal point behind )

focal point

the point where rays gather at after reflection or refraction

diverge

spread out

converge

bring in

real image

an optical image formed when light rays from an object actually intersect or converge at a point, typically created by convex lenses or concave mirrors

virtual image

an optical image formed from the apparent divergence of light rays from a point, as opposed to an image formed from their actual divergence.

why do virtual images appear to come from behind mirror

• When light from an object hits a mirror, it reflects and travels to your eyes. The light never goes behind the mirror—it only bounces off the front surface.

• Your brain assumes light travels in straight lines. So it traces the reflected rays backward in straight lines.

medium

an intervening material, environment, or agent through which forces (light, sound), energy, or organisms travel, are cultivated, or are preserved

refracted ray

the path of light that bends as it passes obliquely from one transparent medium into another

angle of refraction

angle between the normal and the refracted ray

why does the image appear ti be in a different position when it refracts

When light moves between materials (like air and water), it bends (refracts). Your brain assumes light travels in straight lines, so it traces the bent rays backward in straight paths. This makes the object appear in a different (shifted or shallower) position than it really is.

why some substances refract light more than others

Denser substances have more particles packed closely together, so light interacts with more particles and slows down more. This greater slowing causes the light to bend more, so denser materials refract light more than less dense ones.

concave lens

thinner in the centre than edges

convex lens

curves outward and thicker in the middle

digital image

a representation of a two-dimensional image, such as a photo or scan, as a finite set of digital values, called pixels

charged coupled device ( CCD )

A light-sensitive integrated circuit that acts as an image sensor, converting photons into electrons to create digital images.

What is the difference between images with small pixels vs large pixels?

Images with small pixels have higher resolution and more detail because there are more pixels per area. Images with large pixels have lower resolution and look more blocky or blurry.

How do computers store images?

Computers store images as a grid of pixels, where each pixel is represented by numbers (binary code). These numbers store color and brightness values (like RGB values).

How are digital images captured?

Light enters a camera and hits a sensor. The sensor detects the light and converts it into electrical signals, which are then turned into digital data (numbers) to form an image.

How is a CCD used to create a digital image?

A Charge-Coupled Device (CCD) sensor is made of tiny light-sensitive cells. Each cell detects light and converts it into an electrical charge. These charges are read and converted into digital values, creating pixels in the image.

How are digital images transmitted?

Digital images are sent as binary data (0s and 1s) through networks (like the internet). The data is often compressed to reduce file size, then sent and reconstructed on the receiving device.

wavelength

distance from 1 crest to another or trough (bottom)

amplitude

height from rest position to the crest (top)

frequency

number of times the medium vibrates in a given unit of time or herta

visible light spectrum

when white light refracts and splits into different colors of a rainbow
- different color = different wavelength

• shorter wavelength = higher energy