LIGHT notes

Define refraction and describe the reason for it

• bending of light as it travels from one medium to another

• reason: since speed of light is different depending on the medium, the light ray will change its direction unless it travels along the normal

what is the equation associated with speed of light and index of refraction?

index of refraction → n = c/v → speed of light in a vacuum/speed of light in medium

what happens to the refracted beam of light as it exits from low index to higher index of refraction?

the refracted beam of light will move towards the normal (smaller angle) since it’s going from high speed to low speed ex. air to glass

what happens to the refracted beam as it exits from high index to low index of refraction?

refracted beam of light will move away from normal (larger angle) since it’s going from low speed to high speed ex. glass to air

what happens to the refraction beam of light as the incident angle gets bigger (from higher to lower index)?

the refraction beam bends away from the normal and becomes greater than the incident angle until i reaches the critical angle, then total internal reflection happens

define critical angle

occurs when the refracted angle is 90 degrees to the normal

what happens once the critical angle is achieved

when you go past the critical angle… you will get total internal reflection

• light can’t enter the new medium anymore and it acts like a mirror

equation for snell’s law

n_isin theta_i = n_rsin theta_r

discuss the position of the object relative to the image observed as one looks into water (at an angle)

objects appears closer to the surface and shallower than its actual location (virtual image that our eyes perceive)

describe what wavelengths of light disperse greater when white light travels through prisms

shorter wavelength (violet) bends more toward the normal while longer wavelength (red) bends away, out of the high index

• then when it leaves prism, they are opposite positions

Define converging lens, diverging lens, and the common names for both

• converging: also known as CONVEX lens, thicker in the middle than the sides

• diverging: also known as CONCAVE lens, thinner in the middle than the rims

Convex lenses: write out where and orientations of the images in relation to the object (distance). Determine whether images are virtual or real (outside vs. inside)

• converging lenses can produce real or virtual images of real objects

• when the object is outside of the focal point, convex lens is real and inverted

• when object is inside focal point, lens is virtual and upright

Concave lenses: write out where and orientations of the images in relation to the object (distance). Determine whether images are virtual or real (outside vs. inside)

• diverging lenses produce virtual images of real objects

• image created by lens is ALWAYS virtual and smaller

• focal point is ALWAYS -f

Describe where an image falls on the retina of a normal sighted, near sighted (myopia), and far sighted (hyperopia)

• normal sight: incoming rays fall directly on the retina bc length of eyeball matches bending of cornea and crystalline lense perfectly

• myopia: light rays fall in front of the retina bc the eyeball is too long from front to back or the cornea has too much curvature, you can’t see things afar (light rays scatter before it hits eye)

• hyperopia: light rays fall behind the retina bc the eyeball is too short or the cornea is too flat, near objects are blurry bc light hits retina before it can converge into sharp point

Which lenses can correct myopia (near sighted) and hyperopia (far sighted)

• myopia: concave lens (thinner in the middle than sides) which spreads the incoming light rays outward before it hits the retina, pushing the final focal point back

• hyperopia: convex lens (thicker in the middle than sides) which bends the light rays more sharply so they hit the retine instead of behind it, shortening focal point

Discuss how many lenses and what they do in microscopes, astronomical telescopes and terrestrial telescopes.

• microscopes: only 2 primary lens to magnify tiny, nearby objects

  • objective: closest to specimen, creates magnified, real, and inverted image

  • ocular lens: closest to eye, creates much larger, virtual, inverted final image

• astronomical telescopes: 3 lens from a distant image

  • first strikes the objective lens

  • focuses them into a tiny, bright, upside down real image at the focal point

  • short eyepiece lens: final larger, inverted, virtual image past the focal point

• terrestrial telescope: 3 lens

  • (real, magnified, inverted) → (real, magnified, upright) → (virtual, very magnified, upright)

presbyopia

gradual decline in ability to focus on nearby objects and small print; when the eye’s lens harden and lose its ability to change shape for focusing

List the primary pigments

• they are subtractive

• cyan, magenta, yellow

• mixing all three creates black

for printers, paints

List the primary colors of light

• additive

• red, green, blue

• mixing all three creates white

Describe how additive and subtractive combinations occur

additive - all create white with colors of light

subtractive - all create black with primary pigments

Describe the polarization of light

unpolarized light: natural light with a transverse wave that vibrates in all directions

polarized light: light filtered or reflected so it is uniform

• transmission, reflection, scattering

Describe what patterns occur with diffraction gratings (you do not have to specify between single slit,

double slit, or multi slit diffraction gratings).

it splits and interferes to create a distinct pattern of sharp bright spots called maxima and wide dark regions in between called minima

• rainbow effect, wide, dark intervals, central maximum

• shorter wavelengths result in narrower patterns

Which wavelengths of light diffraction fall further from the central white light.

longer wavelengths of light diffract at wider angles and fall further from central white light

diffraction

bending of light around the corners of obstacle whose size is comparable to wavelength of light