Optics Flashcards
(34 cards)
Nothing can move faster than light. True or false?
True
What is a photon?
A small packet of light energy
Light travels in straight lines. True or false?
True
What does most energy require to be transmitted, that light does not require. Why doesn’t light require this?
A medium - any physical substance that acts as a carrier for the transmission of energy
EX: Heat energy can be transferred through convection (touching).
Light does not require this because it is self-propagating/self-spreading. Light is transferred through radiation, and radiation does not require a medium to transfer energy. You could also say that they travel in a vaccum.
What is light transferred through?
Radiation.
Under certain conditions, light shows wave-like properties. What are these waves called?
Electromagnetic waves
What do all waves have?
Wavelengths, amplitude, frequency electric field, magnetic field, and propagation direction
What is the electric field of a wave?
An invisible force field created by the attraction and repulsion of electrical charges
What is the connection between the electric field and magnetic field or a wave
- The changing magnetic field induces a changing electric field and vice versa
- They are right angles to each other
- They are perpendicular to the direction in which the wave moves
What is the meaning of the amplitude of a wave?
The amount of energy the wave carries (higher amplitude, higher energy)
What is the meaning of the wavelength of a wave
The distance between identical points.
As the wavelength decreases, frequency and, therefore, energy increases
What are some of the different types of electromagnetic waves?
Microwaves, x-rays, visible light
What is the meaning of frequency?
Different frequencies result in different kinds of light.
Frequencies greater than that of visible light include UV rays, X-rays, gamma rays, etc
Frequencies less than that of visible light include infrared radiation, microwaves, or radio waves.
What do you call objects that do and do not produce light
Produce: luminous
DO NOT Produce: non-luminous
What are the different ways in which light is produced? Explain each
Incandescence:
The production of light as a result of high temperature (EX: Fire)
Electric Discharge:
The process of producing light by passing an electric current through a gas (EX: Lightning)
Phosphorescence:
The process of producing light by the absorption of ultraviolet light, resulting in visible light over an extended period of time (EX: glow-in-the-dark toys)
Fluorescence:
The process of producing light by the absorption of ultraviolet light, resulting in visible light over a short period of time (EX: Uranium glass)
Chemiluminescence:
The direct production of light as a result of a chemical reaction with little to no heat produced (EX: Fireflies, glow sticks, and bioluminescent algae)
Triboluminescence:
The production of light from friction as a result of scratching, rubbing, or crushing certain crystals (Rubbing quartz crystals)
Electroluminescence:
The process of producing light occurs when electrons and holes in a semiconductor recombine and release energy in the form of light (LEDs)
What does the colour of light depend on?
It depends on how stretched out the light waves are. Red light has very stretched out waves (longer wavelengths), and blue light have much less stretched out waves (shorter wavelengths)
Why is the sky blue? Why isn’t it so blue when the sun is setting?
When the sunlight into Earth’s atmosphere, it is scattered in all directions by the gas molecules in the air. The types of gases in the Earth’s atmosphere mostly scatter the shorter, choppier waves of blue light.
When the sun is setting, its position lowers. This allows more of the blue light to be scattered away before it gets to you. This allows more of the orange, red and yellow light to pass strait through the atmosphere and to your eyes.
Another cause for a red sky can be high amounts of dust, pollution or smoke particles in the air because these particles also scatter a lot of blue light, leading to a very red sky
Why do we perceive incandescent sources of light as white light?
Because incandescent sources emit light of many different WAVELENGTHS and ENERGY LEVELS. This causes all the colours to blend together, causing us to perceive the light as white light
Lasers emit electromagnetic waves of exactly the same energy level. What does this cause?
Since the lasers emit electromagnetic waves of the same energy level, they produce a very pure colour, and are concentrated in a straight narrow beam.
These properties make a laser light very dangerous (never look into a laser)
What is the Ray Model of Light?
- We illustrate the spread and motion of light using light rays, a straight line and an arrow, representing a straight-line path of light (all light travels in straight lines)
- Luminous objects (like candles) radiate light in all directions
What does it mean when something is transparent, translucent, or opaque?
Transparent: an object through which light passes fully
Translucent: an object through which light is diffused
Opaque: objects that absorb or reflect all light
What are some examples of objects that are transparent, translucent, and opaque
Transparent: Glass, still water
Translucent: Clear plastic, frosted windows
Opaque: Paper, people, wood, and most other things
Plane mirrors, also known as flat mirrors, have glass? What is the purpose of it?
These mirrors have a reflective thin film (this is the part that actually reflects). The glass helps protect the thin film from scratches and dents, while also helping it keep its shape.
What is the definition of normal?
The perpendicular line from the mirror’s surface.
