Physical Science - Light
What are the 7 properties of light?
(1) light is fast, (2) light carries energy and information, (3) light travels in a straight line (4) light can vary in intensity, (5) Light is made up of many different colors, (6) light has both wave and particle properties, (7) light can change direction with interactions with matter
How fast can light travel?
300,000,000 m/s (meters per second) The fastest thing in the universe.
How long does it take sunlight to travel from the sun to the Earth?
8 minutes
How far does sunlight travel from the sun to the Earth?
92 million miles
Theta
A Greek symbol commonly used to represent an unknown angle.
What is the cause of refraction?
A change in light speed; and wherever the light speed changes most, the refraction is greatest.
refraction
A change in the speed of a wave when it passes from one material to another causing light waves to bend
incident ray
A incoming ray (drawn perpendicular to the wavefronts) that shows the direction that light travels as it approaches the boundary.
Optical Density (OD)
A measure of the extent to which a substance transmits light based on the speed of light through a substance.
Index of Refraction
A property of a material that indicates how much the speed of light in the material is reduced compared to the speed of light in a vacuum. It depends on the light's wavelength. Longer wavelengths have smaller indices of refraction.
refracted ray
A ray (drawn perpendicular to the wavefronts) that shows the direction that light travels after it has crossed over the boundary.
rainbow
An arc of colored light in the sky caused by refraction of the sun's rays by rain. It shows light separated into all of its different colors.
What are the conditions that make an incident ray reflect?
An incident ray reflects when light encounters a mirror.
What effect does an increase in the angle of incidence have upon the angle of refraction?
An increase in the angle of incidence results in an increase in the angle of refraction.
As you increase the angle of incidence, what happens to the angle of reflection?
As angle of incidence increases, the angle of reflection increases.
Why is the lens of the eye transparent?
Because light is transmitted without scattering and you can see objects clearly through the lens
When is the angle of reflection and the angle of incidence the same?
During reflection using smooth objects.
What happens white light when it passes through a prism?
Each color of light is bent a different amount. As a result, the white light is split into different colors of light.
What is meant by the term intensity?
How bright or dim light is.
What does the FST rule of refraction and the SFA rule of refraction NOT indicate?
How much bending occurs.
What are the conditions that make an incident ray go across the boundary without reflecting or refracting?
If a transparent object is surrounded by another material with the same index of refraction, the light will not change speed, and won't reflect or refract as it enters the object.
double slit experiment
In modern physics, the double-slit experiment is a demonstration that light and matter can display characteristics of both classically defined waves and particles and is the basis of quantum mechanics.
What happens to light when it hits the boundary of a new medium?
It acts like a wave.
What will happen to light if you rub a mirror with sand paper?
It affect how the mirror reflects light by causing diffuse reflection since the mirror becomes a rough surface.
Why is the benefit of light traveling in a straight line?
It allows us to predict what will happen to the light so we can calculate where the light is going. Light energy is predictable so it can be used in technologies.
How does light interact with matter?
It changes direction. The directional change depends on the boundaries between types of matter. It can be absorbed, reflected, refracted, diffracted.
How does light at like a particle?
It has photons.
What makes a person color blind?
It is an Inherited problem in the development of one or more of the three sets of color-sensing cones in the eye. They might not have a certain cone or might have a smaller percentage of a certain cone.
What is refraction caused by?
It is caused by the change in speed experienced by a wave when it changes medium
Why is a tooth opaque?
It is opaque since it absorbs light, reflects light, and no light passes through it. You can't see through it.
What happens when light hits the surface of a mirror?
It is reflected
What happens when light travels through a transparent or translucent object?
It is refracted because the speed of the light ray changes.
What makes light predictable?
It moves in a straight line.
What is wave-particle duality?
Light acts like particles and waves.
How does light vary?
Light can also vary in intensity.
What happens to light when it interacts with other materials?
Light changes direction.
Refraction happens because . . .
Light changes speed when it hits another material.
How does light carry energy and information?
Light contains packets of energy called photons. Fiber optics are used to send information (ex. phone and cable companies)
How does light vary in intensity?
Light varies in how bright or dim it is.
opaque
Materials only absorbs and reflects light; no light passes through them. It blocks all of the light.
transparent
Materials that transmit light without scattering it, so you can see objects clearly through them. Light travels through.
translucent
Materials transmit light but also scatter it. Light partially passes through.
Were there any times where the angle of incidence was greater than the angle of reflection?
No
opaque
Objects that only absorb and reflect light.
What happens to light in rough objects?
Reflected rays bounce in many directions.
diffuse reflection
Reflection of light waves from a rough surface. It reflects light but does not reflect the image.
Why is skin translucent?
Since it can transmit light and scatter it. You can't see clearly through it. The objects appear blurry.
Why are fingernails translucent?
Since they can transmit light and scatter it. You can't see clearly through them. The objects appear blurry.
What happens if if a light wave passes from a medium in which it travels fast (relatively speaking) into a medium in which it travels slow?
The FST rule of refraction. Then the light wave will refract towards the normal. In such a case, the refracted ray will be closer to the normal line than the incident ray is.
What happens if a light wave passes from a medium in which it travels slow (relatively speaking) into a medium in which it travels fast?
The SFA rule of refraction. The light wave would refract away from the normal. In such a case, the refracted ray will be farther from the normal line than the incident ray.
What is the angle of refraction?
The amount of bending that a light ray experiences = the difference between the angle of refraction and the angle of incidence
Laws of reflection
The angle at which a light wave strikes a surface is the same as the angle at which it was reflected
Were there any times where the angle of incidence was greater than the angle of refraction?
The angle of incidence was always greater than the angle of refraction. This happened with both refraction of light through rectangular prism and refraction of light through semi-circular prism
.Which angles are typically different due to refraction?
The angle of refraction and the angle of incidence.
angle of refraction
The angle that the refracted ray makes with the normal line.
Refraction
The bending of the path of a light wave as it passes across the boundary separating two media.
diffraction
The bending of waves as they moves around an obstacle or pass through a narrow opening or slit. The diffracting object or opening becomes a secondary source of the transmitting wave.
What does the directional change of light depend on?
The boundaries between types of matter called mediums.
What is diffuse reflection?
The idea that light bounces in multiple directions when it hits a rough surface.
What are the conditions that make an incident ray refract?
The incident ray refracts when the light reaches a different material or medium and the waves change speed causing the light to bend.
How does the changing the angle of incidence relate to the angle of refraction?
The larger the angle of incidence is, the larger the angle of refraction will be. .
incident ray
The light that approaches an object
What is the angle of reflection measured against?
The normal line which is perpendicular to the boundary of the new medium.
What are photons?
The smallest unit of light.
lumen
The unit of measurement for how much light is perceived by the human eye.
What does the FST rule of refraction and the SFA rule of refraction indicate?
These two rules regarding the refraction of light only indicate the direction that a light ray bends.
What do fiber optics do?
They send information in telecommunications and can be used to examine the inside of the body.
What are fiber optics?
Thin flexible fibers of glass or other transparent solids that transmit light signals.
Why is light represented as a sine wave?
To show a single frequency, wavelength, phase and polarization.
Why is important that light moves in a straight line?
We can predict how it will interact with matter and we can use it in technologies.
When does light change speed?
When it interacts with a new medium.
index of refraction
a measure of the amount a ray of light bends when it passes from one medium to another
What is white light made of?
all colors
refract
change direction or bend
What can white light also be made up of?
complementary colors
The point of incidence is always:
drawn perpendicular to the boundary
What does light carry?
energy and information
What are two ways that you could direct a light wave around a corner?
interacting with other objects and internal diffraction.
What is the fastest thing in the universe?
light
wave-particle duality
light has properties of both waves and particles
reflect
light slows down when it hits a new material
reflected ray
light that is reflected
Opaque objects
only absorb or reflect light.
What is light made of?
photons
What colors or wavelengths are detected by the 3 specialized cones or cells in the eye's of humans?
red, green, or blue
What are two ways for light to change direction?
reflection and refraction
What helps us see color?
specialized cells called cones
What is the angle of refraction measured against?
the normal line
What is the symbol for the angle of incidence?
theta-i
What is the symbol for angle of reflection?
theta-r
What does light have properties of?
waves and particles
