Light and Optics Flashcards
In order of low to high energy, what are the 7 different kinds of waves?
Radio waves Microwaves Infrared waves Visible Ultra Violet X-ray Gamma ray
What wavelengths are found in the visible spectrum and which colors do these extremes coordinate with?
400 nm (violet) - 700 nm (red)
What type of wave are electromagnetic waves?
Transverse waves
How do the oscillating electric field and magnetic field of electromagnetic waves coordinate in respect to the direction of propagation and each other?
Electric and magnetic field vectors are perpendicular to the direction of propagation and each other
What speed do all electromagnetic waves travel in a vacuum?
Speed of light (c)
3.0E8 m/s
What is the equation that describes the speed of light (or velocity of a wave)
c=fλ
from v=fλ
What color would you see if the light contained all colors in equal intensity?
White
Do objects reflect or absorb the perceived light?
Reflect
What color would you see if a red object was illuminated with green light?
Black
The green light would be absorbed
What is blackbody?
Refers to an ideal absorber of all wavelengths so it would appear completely black if it were at a lower temperature than surroundings
Define reflection
The rebounding of incident light waves at the boundary of the second medium (not absorbed by second medium)
What is the law of reflection?
θi=θr across the normal
What is the normal?
A perpendicular line to the medium boundary in which all angles are always measured against (not the medium)
What is a real image?
When light actually converges at the position of the image
What is a virtual image?
When light only appears to be coming from the position of the image, but does not actually converge here
What type of image do plane mirrors form and how?
Create virtual images because the light is reflected (it never diverges or converges)
Creates the appearance of light rays originating behind the mirror
How does the radius of curvature relate to the focal point?
f=r/2
Where is the center of curvature and radius of curvature located for a concave surface? convex?
Concave: both in front of the mirror
Convex: both behind the mirror
Mirrors vs. lenses
Which are converging and which are diverging in respect to concave/convex?
Mirrors:
converging: concave
diverging: convex
Lenses:
converging: convex
diverging: concave
How do focal point, object distance, image distance, and radius all relate?
1/f = 1/i + 1/o = 2/r
In a mirror, if the image distance is positive, is it real or virtual? What if it is negative?
Positive: real image
Negative: virtual image (behind the mirror)
What is the formula for magnification?
m = -i/o
What does a negative magnification indicate? Positive magnification?
Negative: inverted image
Positive: upright image
What size of image forms if m>1, m=1, or m
m>1 : image is enlarged
m=1 : image is the same size as object
m
If an object is placed between the center of curvature and focal point of a concave mirror, what will the image look like/where will it be?
It will be behind the object, passed the center of curvature
It will be inverted, magnified, and real
If an object is placed at the focal point of a concave mirror, what will the image look like/where will it be?
no image will form because the light lights will come off parallel to each other
If an object is placed between the mirror and focal point of a concave mirror, what will the image look like/where will it be?
The image will be behind the mirror
It will be magnified, upright, and virtual
If an object is placed behind the center of curvature of a concave mirror, what will the image look like/where will it be? What happens as it gets further and further from the mirror?
The image will appear inverted, reduced, and real
Always located between the center of curvature and the focal point
As it gets further away, the image gets smaller and closer to the focal point
What image forms from a diverging mirror (convex)? What happens to the image as the object distance gets further away?
Only forms virtual, upright, reduced images regardless of position
Further away the object, the smaller the image
In terms of mirrors, what does a positive r or f value represent? Negative r or f value?
Positive: converging (concave)
Negative: diverging (convex)
What is refraction?
The bending of light as it passes from one medium to another and changes speed
How does the speed of light through a medium compare to through a medium?
Speed of light through a medium is always less than through a vacuum
How do you find the index of refraction?
n=c/v
What is the equation for Snell’s Law?
n1 sinθ1 = n2 sinθ2
When measuring the angle for refraction, what is θ measured from?
Angle between refracted light and the normal
What is the normal?
Imaginary line perpendicular to the surface in which θ is measured against
If the n (index of refraction) increases, how does the angle change? What if n decreases?
As n increases, the angle decreases (bends toward the normal)
As n decreases, the angle increases (bends away from the normal)
What is the critical angle?
When light travels from an area of higher index of refraction to a lower index of refraction, the incident angle can increase to an extent that the refracted light will equal 90 degrees
What is total internal reflection?
when a propagating wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface and the light is reflected back
How many focal points do lenses have?
Two - one on each side
What is the Lensmakers equation for when the thickness of the lens cannot be neglected?
1/f = (n-1) (1/r1 - 1/r2)
r = radius of curvature of each lens surface
What kind of lenses should someone who is nearsighted wear? What about farsighted?
Nearsighted: diverging
Farsighted: converging
What does a positive image distance mean for lenses? Negative image distance?
Positive: Real and opposite side of lens
Negative: Virtual and same side of lens
What does positive r and f values mean for lenses? Negative r and f values?
Positive: converging lens (convex)
Negative: diverging lens (concave)
What is the equation for power of lenses?
P = 1/f
in meters
How do lenses in contact affect the focal length?
Behave as a single lens with equivalent focal length
1/f = 1/f1 + 1/f2 + 1/fn
What is hyperopia? What lens would be needed?
Farsightedness
Need converging lens
What is myopia?
Nearsightedness
Need diverging lens
What is the total magnification of lenses not in contact?
m = m1 x m2 x mn
What is the object for the second lens for lenses in series not in contact?
The image of the first lens in the object of the second lens, etc.
The image of the last lens in the image of the system
What is dispersion?
When various wavelengths of light separate from each other
When white light is dispersed….where do the extreme colors go and why?
Violet is always on the bottom because it experiences the most amount of refraction due to its smaller wavelength
Red is always on top because it experiences the least amount of refraction due to its larger wavelength
What is diffraction?
The spreading out of light as it passes through a narrow opening or around an obstacle
What occurs in a single slit diffraction system? What happens if the slit gets smaller?
Light waves spread out
If the slit gets smaller, the light spreads out more
What pattern appears on a slit-lens system? What happens as the slit becomes narrower?
A bright central fringe (maxima) with alternating dark and bright fringes on each side
Central fringe is twice as wide as fringes on either side
As slit becomes narrower, the central fringe gets wider
What is the equation to find the location of dark fringes on a slit-lens system?
a sinθ = nλ
a=width of slit
θ= angle between line from center of lens to the dark fringe and the axis of the lens
n=fringe number
λ= wavelength
What pattern is observed from multiple slits system?
Interference pattern is observed alternating from constructive interference (bright fringes) and destructive interference (dark fringes)
What is the equation to find the location of dark fringes on a multiple slit system?
d sinθ = (n + 1/2) λ
d=distance between slits
n=fringe number
θ= angle between line from center of lens to the dark fringe and the axis of the lens
λ= wavelength
