Ch 8 - Lights and Optics Flashcards
What are electromagnetic waves?
transverse waves that consist of an oscillating electric field and an oscillating magnetic field
- the 2 fields are perpendicular to each other and to the direction of propagation of the wave
c = f x lambda
What is the electromagnetic spectrum?
- the range of frequencies and wavelengths found in EM waves
- from lowest to highest: radio, microwaves, infrared, visible light, UV, xray, and gamma
What wavelength does the visible spectrum run from?
approximately 400 nm (violet) to 700 nm (red)
WHat is reflection?
the rebounding of incident light waves at the boundary og a medium
What is the law reflection?
states that the incident angle will equal the angle of reflection, as measured from the normal
What are the components of a spherical mirror?
they have centers and radii of curvature and focal points
What are concave mirrors?
- converging systems and can produce real, inverted images or virtual, upright images, depending on the placmeent of the object relative to the focal point
What is a convex mirror?
diverging systems and will only produce virtual, upright images
What are plane mirrors?
- produce virtual, upright images
- these images are always the same size as the object
- may be thought of as sperical mirrors with infinite radii of curvature
What is refraction?
the bending of light as it passes from one medium to another
What does changes in the speed of light depend on and what causes refraction?
- depends on index of refraction of the medium
- change in speed of light causes refraction
What causes dispersion of light through a prism?
the behavior of the amount of refraction depends on the wavelength of the light invovled
What is Snell’s law?
(the law of refraction)
- states that there is an inverse relationship between the index of regraction and the sine of the angle of refraction (measured from the normal)
n = c/v
n1 = sin(angle1) = n2sin(angle2)
When does the total internal reflection occur?
when light cannot be refracted out of a medium and is instead reflected back inside the medium
- this happens when light moves from one medium with a higher index of refraction to a medium with a lower inde of refraction with a high incident angle
angle = sin -1 (n2/n1)
What is the critical angle?
the minimum incident angle at which total internal reflection occurs
What do lenses do?
refract light to form images of objects
Where are the focal points on thin symmetrical lenses?
on each side
What is the difference between convex and concave lenses?
- convex: converging systems and can produce real, inverted images or virtual, upright images
- concave: diverging systems and will onoly produce virtual, upright images
What do lenses with non negligible thickness require?
use of the lensmaker’s equation
1/f - (n-1)(1/r1 - 1/r2)
When do converging systems create real, inverted images?
when o > 2f, o = 2f, 2f > o > f
When are the real, inverted images of converging systems different?
- o > 2f: reduced
- 0 = 2f: same
- 2f > o > f: magnified
When do converging systems form no image?
when o = f
When do converging systems form virtual images?
o < f
virtual, upright, magnified
What type of images do diverging systems form?
virutal, upright, reduced for all object distances
What is diffraction?
the bending and spreading out of light waves as they pass through a narrow slit
- may produce a large central light fringe surroinded by alternating light and dark fringes with the addition of a lens
What does interference support?
the wave theory of light
What does Young’s double slit experiment show?
the constructive and destructive interference of waves that occur as light passes through parallel slits, resulting in minima (dark fringes) and maxima (bright fringes) of intensity
What happens in plane-polarized light?
all the light rays have electric fields with parallel orientation
How is plane polarized light created?
by passing unpolarized light through a polarizer
What happens in circulatory polarized light?
all of the light rays have electric fields with equal intensity but constantly rotating direction
How are circularly polarized light created?
exposing unpolarized light to special pigments or filters
What is the order of colors in the visible spectrum?
ROY G BV
red, orange, yellow, green, blue, violet
What follows the same trend as the electromagnetic wave? What is opposite?
frequency has the same trend, wavelent is the opposite
How are the 4 distances of mirrors related?
1/f = 1/o + 1/i = 2/r
What is magnification and how is it calculated?
a dimensionless value that is the ratio of th eimage distance to the object distance
m = -i/o
if |m| < 1: image is smaller than object (reduced)
if |m| > 1: image larger than object (enlarged)
if |m| = 1: image same size as object
Where is the image any time an object is at the focal point of a converging mirror?
the reflected rays will be paralle so the image will be at infinity
How do you find the image in mirrors?
- draw the rays and find where the lines intersect
- ray parallel to axis reflects back through focal point
- ray through focal point reflects back to axis
- ray to center of mirror reflects back at same angle relative to normal
How do the focal lenghts compare between converging and diverging mirrors/lenses?
- converging: always positive
- diverging: always negative
Assumine o is positive, what are the image types possible with a single lens or mirror?
UV NO IR
- Upright images are always Virutal
- No inage is formed when object is focal length away
- Inverted images are always Real
What happens to light when it enters a medium with a higher v lower index of refraction?
- higher: bends towards the normal
- lower: it bends away from normal
How do you find the image in lenses?
- draw the rays and find where the lines intersect
- ray parallel to axis refracts through focal point of fornt face of lens
- ray through or toward focal point before reaching lens refracts parallel to axis
- ray to center of lens continues straight through with no refraction
In mirrors, is the sign convention for o, i, r, f, and m?
- +o: object is in front of mirror; -o: object is behind mirror (extremely rare)
- +i: image is in front of mirror (real); -i: image is behind mirror (virtual)
- +r/+f: mirror is concave (converging); -r/-f: mirror is convex (diverging)
- +m: image is upright (erect); -m: iamge is inverted
In lenses, is the sign convention for o, i, r, f, and m?
- +o: object is on same side of lens as light source; -o: object is on opposite side (extremely rare)
- +i: image is on opposite side of lens (real); -i: image is on same side (virtual)
- +r/+f: lens is convex (converging); -r/-f: lens is concave (diverging)
- +m: image is upright (erect); -m: iamge is inverted
How is power calculated?
P = 1/f (diopters)
How is the location of the the dark fringes (minima) given?
a x sin(angle) = n x lambda
How does the diffraction pattern for a single slit differ from a slit within a thin lens?
- diffraction through a single slit does not create characteristic fringes when projected on a screen, although the light does spread out
- when a lens is introduced into the system, the additional refraction of light causes constructive and destructive interference, creating fringes
What wave phenomenon do diffraction fringes result from?
fringes result from constructive and destructive interference between light rays
How does double slit diffraction and interference differ from single-slit diffracton?
- the image formed during double slit contains fringes because light rays constructively and destructively interfere
- a single slit forms an image of a wide band of light, spread out from its orignial beam
