Unit 8: Electromagnetic Waves, Reflections of Light, and Optics

What is visible light?

range of frequencies that can be differentiated by the human eye

What is the Doppler effect?

change in frequency of light due to the relative motion of the light source

What are the primary colors?

red, green, blue

What color is made from all the primary colors?

white

What color is made from red and green?

yellow

What color is made from red and blue?

magenta

What color is made from blue and green?

cyan

What are the secondary colors?

yellow, magenta, cyan

What color is made from the secondary colors?

black

What are complementary colors?

colors opposite each other on the color wheel

What color is made from complementary colors?

white

What do rods in the eye detect?

black and white and crispness of image

What do cones detect?

color

What is a pixel?

dot of color

What is a property of light?

additive

What is a property of pigment?

subtractive

What are the primary colors of pigment?

red, blue, yellow

What color do the primary colors of pigment make?

black

What does cyan reflect and absorb?

absorbs red and reflects green and blue

What does magenta reflect and absorb?

absorbs green and reflects red and blue

What does yellow reflect and absorb?

absorbs blue and reflects red and green

Why is the sky blue and the sun yellow?

blue light scatters in the ozone layer, leaving behind yellow

Why is the sunset red?

white sunlight refracts and the only color that bends enough to make it around the curvature of the earth are the longest wavelengths

Why is the Caribbean Sea blue?

sky is being reflected off the white sand

What is a property of light?

light has energy

What is the corpuscular theory?

light is a particle called a corpuscle

What evidence did Newton believe made the corpuscular theory true?

light follows a straight line, light can reflect off a surface, light would speed up as it fell

What is the wave theory?

light is a train of waves with the wavefront being perpendicular to the path of the wave and energy being split along the front

What evidence did Huygen believe made the wave theory true?

lights moves in a straight line, light reflects, when there are multiple sources of light, they interfere with each other, light diffracts, light slows down in water compared to air

What is the speed of light in air?

3.0 x 10^8 m/s

What is the electromagnetic theory of light?

light carries energy by splitting it between an electric and magnetic field that is perpendicular to each other

What is the electromagnetic spectrum from lowest frequency and longest wavelength to highest frequency and shortest wavelength?

radio waves, microwaves, infrared waves, visible light, ultraviolet waves, X-rays, gamma rays

What is the frequency and wavelength of radio waves?

10^6 - 10^4 Hz 0.3 - 300 m

What is the frequency and wavelength of microwaves?

10^9 - 10^12 Hz 0.0003 - 0.3 m

What is the frequency and wavelength of infrared waves?

10^12 - 4.3 x 10^14 Hz 7 x 10^-7 - 3 x 10^-4 m

What is the frequency and wavelength of visible light?

4 x 10^14 - 7.5 x 10^14 Hz 4 x 10^-7 - 7 x 10^-7 m (400 - 700 nm)

What is the frequency and wavelength of ultraviolet waves?

7.5 x 10^14 - 10^17 Hz 3 - 400 nm

What is the frequency and wavelength of x-rays?

10^17 - 10^20 Hz 0.01 - 10 nm

What is the frequency and wavelength of gamma rays?

10^20 Hz <100 picometers

What are the types of UV rays?

UV-A, UV-B, UV-C

What is the effect of UV-A on the body?

needed to produce vitamin D

What is the effect of UV-B on the body?

sunburns

What is the effect of UV-C on the body?

skin cancer

How does frequency and wavelength affect light's ability to penetrate objects?

as frequency increases and wavelength decreases, light's ability to penetrate objects increases

What is the exception of higher frequency increasing light's ability to penetrate objects?

UV rays

What is wave-particle duality?

under certain circumstances, photons are emitted and light is created

What is the photoelectric effect?

radiation that causes electrons to be lost from a substance

What frequencies can cause the photoelectric effect?

UV or higher frequencies

Which electrons does light displace first?

electrons near the surface of the object

What is work function?

amount of work needed to remove a photon

What is the formula for energy input when work is involved?

E = W + KE E = energy (J) W = work (J) KE = kinetic energy (J)

What is the Planck equation?

E = hf E = energy (J) h = 6.626 x 10^-34 Js f = frequency (Hz)

What is reflectance?

percentage of incident light that is reflected from a surface

What type of materials have the best reflectance?

smooth, metallic materials

What happens when light encounters a barrier?

gets either scattered, transmitted, absorbed, or reflected

What is specular reflection?

all incident rays come into a barrier in a regular pattern and the outgoing rays are also in a regular pattern

What is diffused reflection?

incident rays come into a barrier and the outgoing rays are in an irregular pattern

What is a plane mirror?

flat mirror

What is a spherical mirror?

curved mirror

What is the normal line of a reflection?

reference line perpendicular to the mirror

What is the angle of incidence?

angle between incident ray and normal line

What is the angle of reflection?

angle between reflected ray and normal line

What is the first law of reflection?

angle of incidence equals angle of reflection

What is the second law of reflection?

all of the light rays (incident and reflected rays) as well as the normal line lie in the same geometric plane

What is an image?

reflection of an object

What is a real image?

occurs when real light rays intersect and is always in front of a mirror and upside-down

What is a virtual image?

occurs when virtual light rays intersect and is always behind the mirror and upright but reversed laterally

What is a front silvered mirror?

metal reflective surface on the front of a piece of glass

What is a back silvered mirror?

metal reflective surface on the back of a piece of glass

What is a convex mirror?

mirror with a surface that curves outward

What is a concave mirror?

mirror with a surface that curves inward

What is the vertex of a curved mirror?

middle of the curve of the mirror

What is the focus of a curved mirror?

halfway point between vertex and center of the circle created by the curve of a mirror

What is the center of a curved mirror?

center of the circle created by the curve of a mirror

What is the principal axis of a curved mirror?

line passing through the vertex and center of a mirror

What is the secondary axis of a curved mirror?

line passing through the center of a mirror but not the vertex

What are the rules of image formation in curved mirrors?

light rays that come parallel to the principle axis are reflected out through the focus (In ∥ Out F), light rays that come in through the focus are reflected out parallel to the principle axis (In F Out ∥), light rays that come in through the center are reflected out the center (In C Out C)

What is the formula for distances of an image created from a mirror?

1/d0 + 1/di = 1/f d0 = distance to object (always +) di = distance to image (real +) (virtual -) f = focal length (concave +) (convex -)

What is the formula for heights of an image created from a mirror?

hi/h0 = di/d0 hi = height of image (real +) (virtual -) h0 = height of object (always +) di = distance to image (real +) (virtual -) d0 = distance to object (always +)

Does the speed of light change when going through different materials?

yes, it slows down in materials other than a vacuum

What is optical density?

inverse measure of the speed of light through a material

What is the formula for optical density?

P0 = 1 / cm P0 = optical density cm = speed of light in that material

What is optical refraction?

bending or speed change that occurs when light passes into a material of a different optical density

What happens if light is coming in perpendicular to a boundary?

only speed changes

What happens if light is coming in at an angle to a boundary?

speed and direction both change

What is the angle of incidence?

angle between incoming light ray and the normal line

What is the angle of refraction?

angle between refracted light ray and the normal line

What is partial refraction/reflection?

light does not completely refract in a material but reflects

What is the formula for index of refraction?

n = cvac / cm n = index of refraction cvac = 3 x 10^8 m/s cm = speed of light in material

What is the index of refraction?

ranking system comparing speed of light in air to speed of light in a specific material

What is Snell's Law?

nisinθi = nrsinθr ni = index of refraction for incident material θi = angle of incidence nr = index of refraction for refraction material θr = angle of refraction

What are prisms?

objects that refract white light into its colors

What is a critical angle?

when refracted ray is along a boundary and creates a refracts angle equal to 90°

What is the notation for a critical angle?

θc

What is the total internal reflection?

when i>θc and causes the ray to reflect

What is the formula for critical angle?

nisinθc = nrsinθr

What condition is required for total internal reflection to occur?

index of refraction of first material is greater than index of refraction of second material

What types of lenses converge light?

convex

light refracts toward the thicker part so light coming in converges

What types of lenses diverge light?

concave