Waves Flashcards
Which type of wavelength diffracts more, Short or long?
The LONGER the wavelength the more the wave diffracts .
What is constructive interference?
When a crest meets a crest or a trough meets a trough and interferes with each other a maximum amplitude is produced. This is called constructive interference.
What is destructive interference?
Destructive Interference is when a crest meets a trough and interferes with each other, minimum or zero amplitude is produced. This is called destructive interference.
How is an Interference pattern created?
regions of constructive and destructive interference produce the interference pattern.
How is a maximum produced?
When 2 wave crests or 2 wave troughs arrive at the same point at the same time, they are said to be in phase. (Constructive Interference).
What is the path difference formulas ?
Path difference = mλ OR
Path difference = (m+1/2)λ
Why are there two different path difference formulas?
At different order maximum’s and minimums the number required at m is different.
( The path difference to the mth maximum) = mλ
m=0 at the central maximum
m=1/2 at the 1st order minimum
m=1 at the first order maximum
m=1 1/2 at the 2nd order minimum ……
What is the Interference equation?
mλ= dsinθ where : m= the order maximum/minimum d = The separation of the slits θ = The angle from the centre to maxima or minima
How do you find the separation of the slits?
Say a grating has 1000 lines per mm
You would take the numerical value for the unit or measurement being used, in this case mm ( 1x10^-3) and you would divide it by the number of lines per that unit measurement, in this case 1000.
Explain the interference of white light?
- The central maximum is white
+ All wavelengths interfere constructively at this point - All other maxima are spectrums . ( ROYGBIV)
- Violet is the closest to the central maximum in EVERY spectrum.
+ Since mλ=dsinθ violet has a smaller wavelength than red so the angle , θ, is smaller for violet than red in EVERY spectrum.
Describe a continuous Spectrum
Continuous spectrum’s have all colours of the rainbow with no gaps
What spectra is produced when elements are heated?
Line emission spectrum
Describe a line emission spectrum.
Individual coloured lines like a barcode on a black background
Describe a line absorption spectrum.
Opposite of a line emission spectrum, black lines like a barcode with a coloured background.
Describe the Bohr model of the atom
- Electrons orbit the nucleus in “discrete” energy levels
The Ionisation Level is furthest from the nucleus and has zero potential energy.
The ground state is closest to the nucleus.
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What happens when electrons lose or gain energy in the bohr model of the atom?
- When energy is given to a gas ( via heat/electricity/light) electrons are excited and move up energy levels
- When electrons lose energy, the fall down energy levels and release photons. ( 1 photon per electron)
What is the equation used to find out energy loss among “discrete” energy levels?
E2-E1 = hf where : E2 = Higher energy level E1 = Lower energy level h = Plancks constant f = Frequency
What is snell’s law?
n = Sinθ1 / Sinθ2 OR Sinθ1/Sinθ2 = λ1/λ2 = V1/V2 where ; θ1 = angle in air ( incidence) θ2 = angle in denser material ( refraction) V = Speed λ - Wavelength YOU CAN mix and match the equation
What is always on the top of the equation in Snell’s law ?
Top of the equation always has the less dense medium regardless of which way the light in travelling.
What will happen when the refractive index gets bigger?
The bigger the refractive index, the larger the change in speed and wavelength.
Frequency will stay the same, no matter what the refractive index is.
What is the critical angle?
The critical angle in glass, is when the refracted ray in air is equal to 90 degrees. ( therefore can’t get any bigger)
What happens when the angle in glass is bigger than the critical angle?
When the angle in glass is bigger than the critical angle, the light is not refracted but is totally internally reflected.
What is the formula for Critical angle?
Sinc=1/n where :
n=refractive index
c=critical angle in glass
What colour is refracted the most?
Short wavelength ( violet) are refracted most.
what is refraction the opposite of ?
Diffraction
What happens to the refractive index depending on the colour of the light?
The refractive index of a substance is higher for short wavelength violet light than it is for long wavelength red light.
What is the difference in the Refraction/Diffraction of different wavelengths? (colours)
Diffraction grating diffracts red light the most
Refraction- violet light refracted the most
Why can Laser light cause eye damage?
Because a laser beam is parallel and has a high irradiance it can cause serious damage to the human eye
