Chapter 1 Flashcards
What is a wave?
A transmission of energy through periodic oscillations, without a net transfer of matter
Define a Transverse Wave
The Particles oscillate perpendicular to the direction of energy flow.
Give an example of a transverse wave that doesn’t require a medium to travel through
Light
Define a Longitudinal wave
The waves move in the same direction (parallel) to the energy flow
Give an example of a longitudinal wave
Sound waves
Difference of Amplitude in Electromagnetic & Sound waves
In Electromagnetic waves, the amplitude (INTENSITY) tells us how BRIGHT the light is
In Sound waves, the amplitude represents the VOLUME, while Frequency is the PITCH
How does the source determine the frequency of a wave?
Wave frequency is determined by how fast the source of the wave is vibrating.
The faster the source is vibrating, the higher the frequency
What is Radiation?
The transmission of energy in the form of electromagnetic waves or high-speed particles
In order of lower to higher frequency, what is the electromagnetic spectrum?
Radio, Micro, Infrared, Visible Light, UV, X-rays, Gamma Rays
Give the percentage of radiation emitted from the sun as infrared, visible light and UV.
Infrared (50%), Visible Light (40%), UV (10%)
Define the refractive index
The ratio of the speed of light in a vacuum to the speed of the medium
What is Total Internal Reflection?
The reflection of all incident light at a boundary between 2 mediums
Explain what happens when light moves into a slower medium with a higher refractive index, such as air into water.
The light bends TOWARDS the normal, thus the angle of refraction will be less than the
What is the formula for the refractive index of a medium
n=c(speed of light in a vacuum)/v(speed of light in a medium)
What is the minimum value for a refractive index
Equal to or greater than 1
What is the formula for refractive indices in 2 different mediums?
n1v1 = n2v2
What is Snell’s Law?
The law gives the formula for light passing between mediums, by relating the refractive index of each medium with the Angle of Incidence and Angle of Refraction
What is dispersion?
Separation of white light into its colours due to different refractive indices for different frequencies
What is a mirage?
An opticul illusion caused by the refraction of light due to changes in AIR TEMP and PRESSURE
What causes a rainbow
caused by the dispersion of the Sun’s light through water in the atmosphere
What is white light?
The Combination of the continuous visible spectrum of electromagnetic radiation
How does dispersion occur?
As different frequencies of light have different refractive indices, when the rays refract, they separate further as you go down
What conditions must be met for rainbows to occur?
- The sun must be behind the observer
- There must be water in the atmosphere (rain droplets)
- The observer must be far away from the water droplets
- Sufficient sunlight reaches the water droplets and reflects light into the observer’s eyes
Explain what happens during a rainbow
Each droplet in a rainbow disperses the whole spectrum of light into a cone, but we dont see the whole rainbow from each drop.
Every drop reflects ONE colour, dependent on its location to our eyes.
The combination of ALL THESE RAINDROPS, EACH REFLECTLING colour int our eyes is the WHOLE RAINBOW
How are mirages formed?
As light moves through air, its speed changes according to snells law, causing the light to REFRACT and change direction.
When the light refracts enough towards an observer’s eyes, a MIRAGE occurs.
They only occur when the air has a RANGE OF temperatures and densities
for instance, surfaces the heat up easily such as roads transfer heat energy to the air, which creates a GRADIENT of both AIR DENSITY and TEMPERATURE above the road
In Summary, the rays that travel through the temperature gradient change speed, thuis bending continuously with the change in temp utnil either TOTAL INTERNAL REFLECTION OCCURS OR THE LIGHT BENDS ENOUGH TO TURN INTO THE OBSERVER’S EYES.
What do Optical Fibres do?
They use total internal reflection to TRANSPORT LIGHT through a cable from one l;ocation to another
Why do we use optical fibres to communicate?
Because they can TRANSFER DATA USING A LARGER RANGE OF FREQUENCIES, making it omre efficient for transferring large amounts of data fast.
Define Total Internal Reflection
Refers to the situation when the incident ray cannot transmit or refract light into the other medium, and occurs when light travels from a higher refractive index medium to a lower refractive index and the angle of incidence is larger than the critical angle
Define Critical Angle
Refers to the angle of incidence when the angle of refraction is 90 degrees
