Physics Test: Light and Optics
Terms in this set (164)
Transverse weaves consisting of oscillating electric and magnetic fields at right angles to one another
Light energy that is emitted by vibrating electric charge
What type of wave has the longest wavelength and lowest frequency?
What type of wave has the shortest wavelength and highest frequency?
Types of waves in order of shortest wavelength/highest frequency to longest wavelength/lowest frequency?
gamma rays, x-rays, uv rays, visible light, infrared waves, microwaves, radio waves
What color has the shortest wavelength and highest frequency?
What color has the longest wavelength and lowest frequency?
What is the only wave that we can see?
The range of frequencies of the EM spectrum that stimulates the retina of the human eye (what we see)
Dual nature of light means that light can behave as both a _ and a _
Who discovered (or this person's work was used to discover?) the dual nature of light?
The dual nature of light was discovered through Einstein's...
Massless bundle of EM energy
What is the speed of light in a vacuum?
What is faster than the speed of light?
Fix the formulas v=fλ and D=vt to include the speed of light
c=fλ and D=ct
Bodies that emit light (looking directly at the source)
What is an example of a luminous object?
Bodies that reflect light
What is an example of an illuminated object?
the moon and all objects on earth
An object that is _ transmits all light through clearly without distorting images
What are 2 examples of transparent objects?
An object that is _ absorbs light and turns it into heat energy
What is an example of an opaque object?
An object that is _ transmits some light but objects are distorted
What are 2 examples of something that is translucent?
frosted glass, shower door
What 3 possible things could happen when light strikes an object?
light wave could be absorbed by the object in which case its energy is converted to heat, light wave could be reflected by the object, light wave could be transmitted through the object
Objects have a tendency to selectively _, _ or _ light of certain frequencies
absorb, reflect, transmit
We (see/don't see) colors that are absorbed
Color spectrum (visible light)
All colors of light are combined; not separated into wavelengths (reflects all colors)
White (reflects/absorbs) all colors
The absence of light
Black (reflects/absorbs) all colors
Primary colors of light
red, green, blue
What happens when you combine all primary colors
you get white light
cyan, yellow, magenta
What are the two ways to see color?
color by reflection and color by transmission
_ in things cause light to absorb certain colors and reflect others
Colors that are reflected you see, colors that are absorbed you don't see
color by reflection (addition)
What is reflected and what is absorbed in a blue shirt?
ROYGIV absorbed, blue reflected
Can you draw the color thing (three circles)?
Colors that are transmitted (pass through) you do see, colors that are absorbed, you don't see
color by transmission (subtraction)
Explain color by transmission in a red filter
absorbs OYGBIV but transmits red so we see red
Light waves are randomly _
When particles vibrate up and down it is _ polarized
When particles vibrate side to side it is _ polarized
This blocks incoming light
filter (polaroid filter)
A 100% polaroid filter will block _% of the intensity of the incident light which means that all of the light will be in _ direction(s), horizontal or vertical
Two 100% polaroid filters held parallel to one another will block _% of the incident light
50 (blocking light in one direction)
Two 100% polaroid filters held perpendicular to one another will block _% of the incident light
100 (blocking light in both directions)
Do you understand the picket fence analogy for understanding polaroid filters?
Glare is _ly polarized
Sunglasses are _ly polarized
vertically (don't let the glare through)
What is meant by the dual nature of light?
wave or particle
Who was the first to prove that light was a particle?
A light wave has two components, what are they?
electric and magnetic fields
What is the source of all electromagnetic waves?
vibrating electric charge
What is the relationship between frequency and wavelength in the electromagnetic spectrum?
Describe two ways to increase illumination of a surface
decrease distance, increase intensity (power and energy)
Describe how light travels
long distances, straight lines, constant velocity, all directions
What happens when light hits a particle
absorbed, reflected, or transmitted
In what two ways does light enter our eyes?
looking at the source (luminous), reflection off of objects (illuminated)
What happens to the intensity of light when it passes through a horizontal polarizer? Two horizontal polarizers? A vertical polarizer, both horizontal and vertical?
cuts intensity in half, half, cut in half, 0
Does the speed of light change as it goes through matter?
yes, slows down
What happens to the speed of light when it leaves matter?
Who was the first person to discover light was the combination of colors?
Explain color in terms of frequency, absorption, and reflection
don't see colors that are absorbed, see colors that are reflected or transmitted
Light is returned by a mirror's surface into _
Usually waves are partly _ and partly _ when they fall on transparent medium
Did you look through and understand the pictures in the reflection and refraction packet?
The bouncing back of a particle or a wave that strikes the boundary between two media always back into the same medium
The angle of incident equals the angle of reflection. Incoming light will bounce off a surface at the same angle it hit the surface
law of reflection
What does the law of reflection say?
angle of incident equals angle of reflection
Angles are measured with respect to a _ line
A normal line is _ to the surface
Is there a change in speed, frequency, or wavelength of a reflected light ray?
Do all objects reflect some light that falls on them or do some reflect nothing?
all objects reflect some
Why can we see illuminated bodies and observe their texture and color and distinguish them from their surroundings?
because all objects reflect some light that falls upon them
Reflection of light in many directions by a rough surface
Incident parallel rays hitting a smooth surface cause the reflected ray to be parallel as well
Rays of light are reflected from the mirror in _ directions
all (infinite # of rays obeying the law of reflection)
Some mirrors produce _ image (plane mirrors)
Light does not actually start at the image
Light can be projected onto a viewing screen
Are our eyes able to tell the difference between an object and its virtual image? If so, how?
The bending of light as it passes at an angle from one medium to another medium
What is the cause and effect of refraction?
cause - light travels at different velocities in different mediums. effect - changes direction or bends from one medium to another
Used to determine the angle at which light will refract from one medium to another
The ratio of speed of light in a vacuum to the speed of light in a certain medium
index of refraction
What is the index of refraction for air? Is this fast or slow?
If the index is higher, the speed of light is _
If the index is lower the speed of light is _
When light is going from low index to high index (less dense to more dense) light bends _ the normal. Example?
towards, air into glass
When light bends towards the normal θi (>, <, =) θr
When light bends away from the normal θi (>, <, =) θr
When light is going from more to less dense, light bends _ the normal. Example?
away from, glass into air
The complete reflection of light at a boundary between two transparent media; light must be traveling from more (slow) to less (fast) dense mediums to occur
total internal reflection (TIR)
The minimum angle of incidence at which TIR will take place
critical angle (θc)
The _ angle is different for different materials but the θr is always _ degrees
Angle of refraction at the critical angle
Any ray that reaches the surface of water at an angle greater than the critical angle will be _
Any ray that reaches the surface of water at an angle less than the critical angle will be _
Used to guide light over a long distance using the process of TIR (keeps light in the _?_)
What are fiber optics (physical makeup) and where are they used?
thin glass fiber coated with a layer of glass with a low index, used in communications, medicine, computer
The process of separating white light into its component wavelengths (colors)
Disperse white light into visible spectrum
Use TIR and dispersion to form rainbows
Which color bends the least? most?
red least purple most
Eye perceives light coming from objects in a _ line
How is apparent depth (image) in relation to actual depth (where it actually is)?
The incident ray, reflected ray, and the _ all lie in the same plane
The property of a medium that determines the speed of light in the medium
index of refractin
_ occurs at the boundary between two media because the speed of light is different in the two media
The Dutch scientist, _, discovered the relationship between the angle of incidence and the angle of reflection
The _ of any substance is the speed of light in a vacuum divided by the speed of light in that substance
index of refraction
When a ray of light passes from glass into air, it is bent _ the normal
When a ray of light enters a medium in which it travels more slowly, the refracted ray bends _ the normal
The _ angle is the angle of incidence that causes the refracted angle to lie along the boundary of the substance
Fiber optics is a practical application of _
Mirages are caused by the _ of light
The dispersion of sunlight from thousands of water droplets in the air produces a(n)
When a sound wave reflects, its echo has a different amplitude. When a light wave reflects, what changes?
Did you study the "understanding concepts" sheet in the "reflection and refraction" packet?
List the seven different colors of the visible light spectrum in order of increasing frequency. How does this list compare to wavelengths
State the law of reflection
In a diagram that shows how a ray of light passes from a fast medium to a slow medium, does it bend away from or towards the normal?
In a diagram that shows how a ray of light passes from a slow medium to a fast medium, does it bend away from or towards the normal?
What causes refraction?
light changes speed in different mediums (refraction is the result of different wave speeds)
Does a light ray that is perpendicular to a surface refract?
no (has to be incident at an angle)
Did you review the reflection and refraction concept questions number 7
Nicole sees a fish in a lake. Which is greater, the apparent depth or the actual depth of the fish?
Which type of reflection occurs off a brick, special or diffuse? Off a mirror? Which type of reflection is more common?
diffuse off brick, specular off mirror, diffuse
What is the definition of the critical angle?
angle of incidence causing TIR (only occurs if going from slow to fast)
If a ray of light is incident at an angle less than the critical angle, what happens?
Refracts away from normal into the medium
If a ray of light is incident at the critical angle what happens?
refracts at 90 degrees
If a ray of light is incident at an angle greater than the critical angle, what happens?
reflects back into the same medium at the same angle (TIR)
Piece of glass (and silver) which reflects (bounces back) parallel rays of light
Type of mirror where parallel rays converge through a focus (focal point)
Type of mirror where parallel rays diverge from a focus (focal point)
Type of mirror where light rays do not converge or diverge
Piece of glass which refracts (bends) parallel rays of light as they pass through
Type of lense where parallel rays converge through a focus (focal point)
Type of lense where parallel rays diverge from a focus point (focal point)
The point at which a beam of light converges or diverges from
The distance from the lens/mirror to the focal point (half of the center of curvature)
Shows how curbed the mirror/lens is
center (radius) of curvature
Formula used (and given) to find the center of curvature
The factor of change in size between the object and image
What is the unit for magnification?
What does it mean if M>1? M=1? M<1?
bigger, same size, smaller
What does it mean if M is positive? Negative?
upright and virtual, negative is inverted and real
Light does not actually start from image
Image that is not projected on a screen and is always upright
Light does actually start from image
Image that can be projected on a screen and is always inverted (upside down)
What are ray diagram rules used for?
to find the location and size of an image
Type of ray that leaves the top of the object and travels parallel to the axis
parallel (principle) ray
Type of ray that leaves the top of the object and travels through the focal point of the mirror
Type of ray that leaves the top of the object and travels to the center
Do you know what lens and mirrors look like (converging vs diverging and concave vs convex)?
Rules for ray diagrams for mirrors
1. parallel in, reflect, through/from focal point 2. through/from focal point, reflect, out parallel 3. stop at intersection (if no intersection backtrace reflected/refracted rays)
Ryles for ray diagrams for lenses
1. parallel in, refract, through/from focal point 2. straighten through center, no bend 3. stop at intersection (if no intersection backtrace reflected/refracted rays)
When Hi is positive is the image real or virtual? If Hi is negative?
positive upright virtual, negative inverted real