3) Waves Flashcards
Formula for refractive index
Speed of light in a vacuum / Speed of light in a medium
Formula for refractive index with angles
Sin i / Sin r
Formula for critical angle/refractive index
n = 1/sin c
What is refraction?
Refraction : The bending of light when it passes from one medium to another
Properties of a mirror image
Same size
Laterally inverted
Same distance from the mirror as the object from the mirror
Characteristics of refraction
1) A ray of light is bent towards the normal when it enters an optically denser medium at an angle, for example from air to glass. The angle of refraction r is less than the angle of incidence i.
2) Away from the normal as it emerges from the denser medium.
3) The incidence ray is parallel to the emergence ray
4) A line perpendicular to the surface of the medium or travelling along the normal line is not refracted.
Why is light refracted?
its speed changes when it enters another medium.
The more refracted the … The less refracted the …
Slower, Faster
Total Internal reflection
When the angle of incidence is above the critical angle and all light is reflected inside the denser medium.
What is an optical fibre
An Optical Fibre is a thin rod of high-quality glass
Light can be trapped by total internal reflection inside a bent glass rod and ‘piped’ along a curved path
Convex = … Concave = …
Converges, diverges
What does it mean when a convex lens is more curved?
the smaller is f and the more powerful is the lens
Image formation rules
- Through F should be parallel to the principal
axis - Parallel to the principal axes should become toward the F.
- A light passing through C will not change through the lens.
Beyond 2F
Smaller, Vertically inverted, between f and 2f
at 2F
Same size, Vertically inverted, at 2F
between F and 2F
Larger, vertically inverted, Beyond 2F
Between F and lens
Larger, Upright, same side of the object
How much light can a mirror reflect
95%
What is a critical angle?
When a ray of light is travelling from a more dense to a less dense medium and the angle of refraction is 90’.
What colour is the sun?
The sun is essentially all colours mixed together, so it is white
What is dispersion?
When light is split into a spectrum and refracted/the splitting of white light into a spectrum.
Polychromatic? Monochromatic?
Poly chromatic is a mixture of different colours, such as white light, and mono is a single colour, like lasers.
Use for radio waves
Radio & television & comms
Use for microwaves
Satelite, tvs and telephones
Use for x-rays
Medicine, security
Use for infrared
Electrical appliances, remote controllers for TVS
As we go down the spectrum, Frequency … and Wavelength…?
Decrease, increase
The larger the frequency, radiation is what
More
How are sounds created
Sounds are created when there is a disturbance in the air or a vibration that travels to our ears.
Why is “sound” a “wave”
Waves are vibrations that travel through a medium or vacuum, if you have a vibration that travels, its a wave, so sound is a wave.
Is sound a longitudinal or a transverse wave
Longitudinal
Longitudinal : ? Transvers : ?
Right left right left/travels to the waves advance
Up down up down, Direction of vibration is perpendicular to the direction of the wave
Compression
A region where particles are pushed together
Rarefaction
A region where particles are further apart than normal
Mechanical waves
A wave that needs a medium to travel through eg. sound waves
Non-mechancial
A wave that doesn’t need a medium, e.g. EM waves
Speed of sound in air
330-350 m/s depending on temperature and humidity of the air
How can we see sound?
oscilloscopes Convert vibrations of air to an electrical signal.
Formula for frequency
f = 1/t or Frequency equals 1 over period
Ultrasound?
Too large humans can’t hear
Infrasound?
Too small that humans can’t hear
