Light and Optics Flashcards
Electromagnetic spectrum
The spectrum that graphs all the electromagnetic radiations of various wavelengths and frequencies.
Describe the visible light spectrum
ROY G BIV
RED = 700nm ( long wavelength, low frequency, low energy)
VIOLET = 400nm ( short wavelength, high energy, and high frequency).
What is the color of an object?
The color of an object is the wavelength that is reflected off of it. All other wavelengths are absorbed.
Blackbody
Object that absorbs all wavelengths and therefore appears completely black.
What type of waves are electromagnetic waves?
Transverse waves. Electric and magnetic fields are perpendicular to each other and to the propagation of the wave ( and thus the energy of the wave).
How to calculate the speed of light?
C= ( frequency)*(wavelength) , where C is 3x10^8. This frequency and wavelength are perpendicular to each other.
What causes refraction and reflection
Waves that travel in a homogenous mixture travel in a straight path called rectilinear propagation. However when it changes media it causes reflection and refraction.
Reflection
The bouncing of the incident wave ( incoming wave) off the media. This creates an incident angle and reflected angle that are equal to each other. Measured with respect to the normal ( perpendicular line to the normal).
Real v. virtual images
Real images formed with light converges at the image. Virtual images are formed with light appears to becoming from the image.
Describe plane mirrors
Only produces virtual images because the light rays reflect off the front of the mirror but the image appears behind the mirror.
Spherical mirrors
They REFLECT light.
Center of curvature is the center point if the mirror created a complete sphere. The radius of curvature is the distance from the sphere surface to the center of curvature.
For concave and convex mirrors where are the center of curvatures and radius of curvatures located?
For concave( converging) mirrors they’re located in front. For convex ( diverging) mirrors they’re located behind.
What is the focal length (f)?
The distance between the focal point ( F) and the mirror.
To find the focal length we take 1/2 of the radius of curvature.
How to determine if an image is real or virtual?
We calculate the image distance. If it’s positive the image is in front of the mirror and real. If it’s negative the image is behind the mirror and is virtual.
What does the magnification tells us?
Whether an object is upright or inverted, or if it’s enlarged or reduced. Dimensionless value so no units.
Calculated by dividing image of distance ( multiplied by negative value). Or the height of the image divided by the height of the object.
What does it mean when the magnification is positive, negative? Larger or smaller than one?
If m is positive the image is upright if m is negative the image is inverted. If the absolute value of m is greater than one the image is enlarged compared to the object. If absolute value is less than one the image is reduced compared to the object.
What does it mean when O is positive, negative?
What about i?
Positive- object is in front of mirror.
Negative- object is in behind mirror.
Positive- image is in front of mirror. Negative- image is behind mirror.
What happens we r is positive, negative? What about f?
If r or f is positive than the mirror is concave ( converging).
If r or f is negative than the mirror is convex ( diverging).
How do we relate speed of light in a vacuum ( C), speed of light in medium ( V), and index of refraction (n)?
n= c/v
Snell’s law
Relates the index of refraction and angles of both incident rays and incident rays.
Total internal refraction
When light moves from a medium with higher index of refraction to medium with lower index of refraction you can get all the rays refracted back into the medium. The angle at which this occurs is the critical angle ( refracted angle) and is 90 degrees.
How does lenses differ from spherical mirrors?
Lenses refract light while mirrors reflect it.
- For lens there are 2 focal points and 2 focal lengths. Each on the other side of lens, the focal lengths are the same distance on either side.
Describe the shape of diverging lens v. converging lens
- Diverging lens are narrow in the center but wide at the edges.
- Converging lens are wide at the center and narrow at the edges.
Lensmaker’s equation
Used for real lenses in which the thickness cannot be negligible.
What happens when the O and i is positive, negative for lens?
If O or i is positive the object or the image will be on the same side of the light source.
If O or i is negative the object or image will be on the opposite side of the light source.
What happens when r or f is positive, negative?
- Positive means the lens is convex ( converging).
- Negative means the leans is concave ( diverging).
Describe real v. virtual images for lens.
- Real images for lens will be on the opposite side the light source.
- Virtual images for lens will be on the same side of the light source.
Power
1/f ( focal length in meters)
Myopia v. Hyperopia
- Myopia is nearsightedness ( see close objects but not objects far away) and require diverging lens.
- Hyperopia is farsightedness ( see objects far away but not close up) and require converging lens.
How to find focal length and power for lenses in contact?
Lenses in contact has the the same focal length and acts as a single lens system.
for focal length: 1/f=1/f1+1/f2+1/f3+…
for power:
P=P1+P2+P3+…
How to find magnification for lens not in contact?
Multiply all of the magnifications.
Mirrors and lenses that are not perfect can cause errors in images. What is this called? What are the 2 types?
Aberrations
- Spherical abberations- light is not refracted or reflected at the edges of the lens or mirror correctly causing blurriness around the periphery of the object because the rays don’t exactly cross at the same spot.
- Chromatic aberrations- rainbow effect around images cause by dispersion of spherical lens.
Dispersion
The splitting of light rays when shined through a prism. Caused by the refraction of the different wavelengths that make up the light
Diffraction v. Interference
Diffraction is the spreading out of light when it moves through a slit or around an object.
Interference is the interaction of these diffracted light rays to create fringe patterns.
How to find the location of a dark fringe for single slit system
Use the following equation:
(a)(sin theta)= ( n) ( wavelength)
a- width of slit
sin theta - angle between the central axis and line drawn to dark fringe.
n= number of dark fringe we’re examining.
wavelength = the wavelength of the incident ray.
Young’s double- slit experiment
Proved that light has wave properties.
Diffracted light between 2 slits and they interacted ( interference) with each other to create a fringe pattern.
How to determine the position of dark fringes for a multiple slit system?
(d)( sin theta)= ( n + 1/2) ( wavelength)
Constructive interference v. Destructive interference
Constructive interference is when diffracted rays interact in such a way that their peak to peak adds up and trough to trough adds up resulting in a bright fringe.
Destructive interference is when diffracted rays interact in such a way that peak lines up to trough and they create dark fringes.
Diffraction gratings
Multiple slit system arranged in a pattern ( DVDs are an example).
Plane- polarized light
Light in which all of their electric ( and therefore magnetic) fields are in the same direction ( parallel).
- Enantiomers rotate plane polarized light in opposite directions cancelling it out.
