Optics Unit 2 Flashcards
Define: Additive Colour Theory
states that white light is composed of the different colours of visible light. White light is produced by combining the primary colours of light: red, green and blue
Define: Amplitude
the lowest point in a wave of light
Define: Bio-luminescence
the ability if a plant or animal to produce light (created by a chemical reaction or naturally carried)
Define: Chemiluminescence
light that is produced through a chemical reaction without rising the temperature
Define: Crest
the highest point in a wave
Define: Diffuse Reflection
a reflection off an object with an uneven surface so the rays of light are reflected in many different angles
Define: Electroluminescence
producing light by passing electricity through a gas (AKA Electric Discharge)
Define: Radiation
energy travelling in the form of waves
Define: Electromagnetic Spectrum
the spectrum of the different types of light rays and the amount of energy they carry
Define: Fluorescent
the immediate emission of visible light as a result of the absorption of U.V. light
Define: Frequency
the rate of repetition of a wave
Define: Dispertion
the refraction of white light into all colours
Define: Electromagnetic Radiation
is a radiation where a wave pattern made of electric and magnetic fields travel through empty space
Define:Gamma Rays
they are the light waves with the highest frequency therefore they are the most dangerous to humans because they carry the most amount of energy
Define:Incandescent
when a substance gives off light because it is very hot. This type of light is very inefficent becuase it only puts 5% of its energy into light and 95% into heat
Define: Infared Waves
are waves with wave lengths just shorter than visible light and they are often used for short-range communication
Define:Light-Emitting Diode (LED)
an electroluminescent light source made of a semi-conductor (a material that can be made to change how well it conducts electricity). LED’s are very efficent and rugged and can be found in electronic billboards, traffic lights, and hand-held displays
Define: Liquid Crystal Display
is a white light that is shone behind a liquid crystal. The liquid crystal changes colour by having a filter in front of it and changing how much electricity passes through and creates pixels.
Define: Microwaves
They are waves of light with a slightly longer wave length than radio waves and are used to heat up food (in a microwave oven).
Define: Opaque
A material that no light can pass through, so all light is absorbed and therefore you cannot see through it.
Define: Phosphorescence
producing light through the absorption of UV light resulting in the emission of visible light over an extended period of time. Ex. glow in the dark stars
Define: Radio Waves
they have the longest wave length and are used for long-distance communications
Define: Ray Model of Light
a diagram used to predict how light will react when it is either absorbed, reflected or transmitted through a surface
Define: Reflect
a throw-back of light off a surface without absorbing the light
Define: Subtractive Colour Theory
A colour theory that applies to pigments which states that the colours are absorbed or “subtracted” from the reflected light that is seen by the eye,therefore we do not see them. Black objects will absorb all colours and white light will reflect all colours
Define: Translucent
A surface where some light can get through it and some cannot, therefore the image that is formed from the light that can get through is blurry or fuzzy
Define: Transparent
A surface that allows all light to pass through and therefore allows for a clear image to be created
Define: Triboluminescence
the production of light as a result of crushing or colliding certain crystals. Ex. wintergreen mints
Define: Trough
the lowest point in a wave
Define: Ultra Violet Rays
are waves that are slightly shorter than visible light so we cannot see them
Define:Visible Spectrum
Refers to the colours of light that can be seen with the naked eye. This consists of Red, Orange, Yellow, Green, Blue, Indigo and Violet (Roy G. Biv)
Define: Wave
A disturbance that transfers energy from one point to another without transferring matter
Define: Wave Model of Light
A way of showing how light travels in waves and how light can react when it collides with something
Define: Wave Length
The distance from one point in a wave to the next similar point in the wave
Define: X-ray
A type of light wave that is longer than UV rays and are most commonly used to take pictures of bones
Define: Magnification
the amount that an image is larger or smaller by. Magnification= image height/object height or image distance/object distance
Define: Medium
any substance that light travels through. It is plural for Media
Define: Normal
a solid or dashed line drawn perpindicular to a mirror at the point of reflection
Define: Optical Device
a device that produces or controls light
Define:Optical Fiber
a very thin glass fiber which light can be refracted through
Define: Plane Mirror
Any mirror that has a flat reflective surface
Define: Real Image
An image formed where light rays actually cross
Define: Refraction
The change in direction of light when it crosses a boundary between two media
Define: Snell’s Law
a formula that uses values for the index of refraction to calculate the new angles that a ray will take
Define: Thin Lens
any lens that has a thickness that is slight compared to its focal length
Define: Vertex
where the normal and the mirror meet in a ray diagram
Define: Virtual Image
any image formed by rays tha do not actually pass through the location of the image
Define: Angle of Incidence
The angle between the incident ray and the normal
Define: Angle of Reflection
the angle between the reflected ray and the normal
Define: Angle of Refraction
the angle between the refracted ray and the normal
Define: Axis of Symmetry
the dashed line dividing a lens in 2
Define: Concave Lens
a lens where the middle is thinner then the ends. AKA a diverging lens
Define: Concave Mirror
a mirror where the edges are ahead of the center (sattelite dish shaped) AKA Converging mirror
Define: Convex Lens
a lens where the ends are wider then the middle. AKA Converging lens
Define: Convex Mirror
a mirror where the middle is ahead of the edges or it bulges. AKA Diverging mirror
Define: Dispersion
the seperation of white light into all colours
Define: Focal Length
the length from the mirror to the focal point
Define: Focal Point
the central point of focus
Define: Image
a reproduction of an object produced by an optical device like a mirror
Define: Incident Ray
the incoming light ray
Define: Index of Refraction
the amount by which a transparent medium decreases the speed of light
Define: Law of Reflection
states that when lightreflects off a surface, the angle of incidence is always equal to the angle of reflection
Define: Lens
The part of the eye that changes shape so that the eye can focus on objects near and far
Define: Pupil
the hole in your eye that allows light into your eye. The size of the pupil is changed by the iris to control the amount of incoming light
Define: Iris
the muscle around th epupil that changes the size of te pupil to allow for more or less light
Define: Cornea
the transparent front part of the eyeball that bends light
Define: Cillary Muscle
muscles that push and pull the lens to focus it by making it thiner or thicker
Define: Viterous Humour
the clear, thick fluid that fills the inside of your eye.
Define: Optic Nerve
the nerve that sends all signals received by the retina to the brain
Define: Blind Spot
the spot where our retina connects to the optic nerve. This means that there is no retina covering this spot therefore there is no image can be seen there
Define: Retina
membrane on the back of the eye containing rod and cone cells which capture images and send them to the brain
Define: Rod Cells
located in the retina and they are sensitive to shades of grey and lowlights so they help us see in the dark
Define: Cone Cells
located on the retina and they are sensitive to bright light and colours so they help us see colour
Define: Far-sightedness
problems seeing things close up
Define: Near-sightedness
problem seeing things far away
Define: Astigmatism
a condition where the cornea has an irregular shape which results in vision problems
What is the order of the electromagnetic spectrum from shortest wave length to longest?
- radio waves
- microwaves
- infrared radiation
- visible light
- ultra violet
- x-rays
- gamma rays
What is Additive Colour Theory?
- states that white light is composed of different colours of visible light
- white light can be produced by combining 3 colours: red, green and blue (the primary colours of additive colour theory)
- by combining any 2 primary colours, you can create one of the secondary colours: magenta, yellow and cyan
- this applies to mixing different lights together
What is subtractive colour theory?
- it applies to pigments
- coloured matter selectively absorbs different wavelengths (colours) of light
- the colours are absorbed or “subtracted” from the reflected light that is seen by the eye
- black objects absorb all colours
- white light reflects all colours
- subtractive colour theory is the opposite of additive colour theory:
- the primary colours are magenta, yellow and cyan
- by combining 2 primary colours, you can get the secondary colours: red, blue and green
What is red made of?
magenta and yellow
What is blue made of?
magenta and cyan
What is Green made of?
yellow and cyan
What is magenta made of?
red and blue
What is yellow made of?
red and green
What is cyan made of?
blue and green
What is luminescence and what are the types of luminescence?
Luminescence is the emission of light by a material or object wihtout using heat or electricity. They inclue:
phosphorescence, fluorescence, chemiluminescence, bioluminescence, and triboluminescence
How do fluorescent light bulbs work?
- they use both gas discharge and fluorescence to create light
- the white powder coating in the bulb fluoresces to make the light more white. They are more efficient than incandescent light bulbs becasuse they convert 20% of their energy into light and 80% into heat.
How does light move?
- it travels in a straight line unless it is changed by the substance it is moving through or if it hits something
- when light is released, it travles out from the source in all directions
What are the 3 things light can do when it hits something?
- Be Transmitted
- Be Reflected
- Be Absorbed
What are the 3 properties an object can be if light is transmitted through it?
- Transparent
- Translucent
- Opaque
What are the steps to draw a ray diagram for a concave mirror?
- draw a line parallel to the normal from the top of the object to the mirror
- continue the line in the opposite direction towards the foacl point
- draw your second line from the top of the object through the focal point until it hits the mirror *if you cannot go through the focal point, go to the vertex and duplcate the angle
- continue the line in the opposite direction, parallel to the normal
- draw your image from the normal to where the rays cross
What are the steps to draw a ray diagram for a convex mirror?
- draw a line from the top of the object to the mirror parallel to the normal
- continue the line out as if it were coming from the focal point
- draw your next line from the top of the obect to the focal point until it hits the mirror
- continue the line parallel to the normal on both sides of the mirror
- draw your image from the normal to where the lines cross from behind the mirror
What are the steps to draw a ray diagram for a concave lens?
- draw a line parallel to the normal unitl the axis of symmetry. Then continue the line through the focal point on the other side
- draw another line straight through the vertex
- draw the last line through the focal to the axis of symmetry then continue in the same direction going parallel to the normal if you cannot go through the focal point, do not draw this line
- draw the image where all lines intersect
What are the steps to draw a ray diagram for a convex lens?
- Draw a line parallel to the normal to the axis of symmetry then continue it away from F’ as if it is coming from F
- draw the next line straight through the vertex
- draw the image where the lines intersect (this should be on the same side as the object)
What is the formula for magnification?
Magnification= image height / object height or image distance / object distance
What is the formula for index of refraction?
I.O.R= sped of light in a vacuum / speed of light in medium or n=c/v
What is the equation for snell’s law?
n1sin(theta)1=n2sin(theta)2
How do you use snell’s law if you are looking for an n value?
- use the formula n=n2sintheta2/sintheta1
- substitute your values and solve
* your sin theta that is missing the value is always on the bottom of the equation*
How do you use Snell’s law if you are looking for an angle?
- use the formula sing theta1= n2sin theta2/n1
- substitute your values and solve
- use the inverse of sin (sin to the -1) with your answer ti get your final answer
What are the rules for a thin lens?
- focal point if it is a concave lens
+ focal point if it is a convex lens - image distance for a virtual image
+ image distance for a real image
What is the thin lens equation to find the focal point?
1/f=1/do+1/di
What is the thin lens equation to find the object distance?
1/do=1/f-1/di
What is the thin lens equation to find the image distance?
1/di=1/f-1/do
What is the range of visible colours from longest to shortest wavelength?
Red Orange Yellow Green Blue Indigo Violet or Roy G. Biv