Optics Flashcards
The sun is ________ from the earth.
1.5 x 10^8 km
How is light produced?
Nuclear reactions within the sun produces lots of energy, expressed in the form of light.
We need the sun to:
- Keep the surface of the earth warm
2. Carry out photosynthesis in land and water ecosystems
Properties of Light
- Travels in straight lines
- Travels in a vacuum
- Transferred by radiation
- Doesn’t require a medium
- Has both electric and magnetic properties
Medium
any physical substance through which energy can be transferred
Conduction (solids) and convection (liquids + gases) require a medium
Photons
Tiny packets of light
Wavelength
Distance from one crest or trough to another
Electromagnetic Waves Properties
- Are not visible
- Travel through a vacuum
- Travel at the speed of light
Electromagnetic spectrum def
Classification system based on the energy of waves
Electromagnetic spectrum order + energy/wavelenth
Radiowaves, microwaves, infrared, visible, UV, x-ray, Gamma
Gets more energy and shorter wavelength
Radiowaves
- Communication in mines, submarines, aircraft
- TV signals, radio, MRI
Microwaves
- Microwaves
- Radar in cars, airplanes
- Satellites
Infrared light
- Image infrared radiation
- Motion sensors, burglar alarms, night vision googles
- Remote control
Visible light
Photosynthesis
Ultraviolet light
- Disinfect water
- DNA analysis
- Reveal substances unseen in visible light
X-Rays
- Medical imaging
- Security in airports
- Photographing in machines to check for damage
Gamma Rays
- Sterilize medical equipment
- Cancer treatment
Visible Light
- Any electromagnetic wave that human eye can detect
- Consists of 7 different colours
- Red has longest wavelength (700 nanometers)
- Violet has the shortest wavelength (400 nanometers)
- Red Orange Yellow Green Blue Indigo Violet (ROY G BIV)
How Do Objects Produce Light?
- Atoms within the object absorb energy
- Atoms are now in an excited state
- Atoms quickly release energy
- Energy sometime released in the form of light
Incandesence: how?
- Light produces when objects are heated to very high temperatures
- Incandescent light bulbs are only 5-10% efficient at producing light, the rest is lost as heat
Incandesence: examples
- Incandesence bulb
- Burning candle
- Stove element
Electric Discharge: how?
- Electricity is passed through gas
- The electricity allows electrons to absorb energy and release it as photons of light
Electric Discharge: examples
- Neon lights
- Lightning bolts
Phosphoresence: how?
Occurs when an object absorbs UV light and returns it for several seconds to days causing them to glow for longer
Phosphoresence: examples
- Glow in the dark
- Dials on wristwatches or clocks
Fluorescence: how?
- Occurs when object absorbs UV light and immediately releases a lower energy light in visible range
- Can provide same light output as an equivalent incandescent bulb but produces less heat and less electricity