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Flashcards in Diffraction Grafting Deck (25):

Exam Question - Explain how the diffraction grafting produces an emission spectrum

the light contains many wavelengths (therefore) the light is diffracted/travels in all directions/paths when it leaves the grating.

the different path difference gives rise to a phase difference in the waves .

if the phase difference is half a wavelength then the waves that meet will cancel out and there is no light/destructive interference .

if the phase difference is a wavelength the waves add/constructive interference .


What is the definition of diffraction

Diffraction this is where light bends around an obstacle or spreading out through small spaces .

If there's a small gap and there's waves coming in on it there will go through the  gap as well as spread out .Go through an object they diffract .The examples of this are light and em waves .


What is diffraction grating ?

Is a flat plan object which has series of regular lines formed on it that blocks parts of the an advancing wave front .


What is the grating for microwaves ?

Microwaves these lines could be a series of regular spaces metal bars or wires .


What is the grating for light ?

You would usually use a piece of glass with a series of very fine and regularly spaced scratches on its surface .You can get a similar effect for X-rays by using the regard spaces rows of atoms and molecules a crystal .


What happens when a wave front meets a diffraction grafting ?

Some of the waves energy continues propagating forward through the gaps between the grating lines .Which is known as transmission
Some of the waves can be absorbed with the remainder of the exams scattered backwards as a reflection .



Wave energy passing through an object such as diffracting grating



Wave energy that bounces off a surface and has its direction of ravel altered by more than 180 degrees .


Path difference

The difference in length between two rays


Why is interference patterns created ?

This Is because of the superposition of waves form separated regular spaces sources coming through the gaps in the diffraction grafting .


What was the young double slit about ?

Were he got a candle which sent light through the diffraction , the slit caused which caused diffraction .

However, he has another two slit which he drew out because he wanted monochromatic coherent light to pass through which means light which has the same wavelength in one colour .

Coherent means the constant phase difference same wavelength and frequency .


What do longer wavelength do ?

Longer wavelength in light diffract more than shorter wavelength which diffract less


What do laser ?

Produce monochromatic coherent light getting the same effect .


What are produced in the screens ?

We have fringes on the screen this is because have interference going which is superposition .


How is bright or dark fringes produced?

1. A path difference is created be dividing a light sources so that's separate ray of light travels in different

2. The difference in path caused by phase difference
3.The path difference increases as the angle through which the grating scatters the light is increased

4. Path difference equals a whole number of wavelengths nλ the light rays will be in phase constructive interference occurs which is a bright fringe .


Spectra - How is spectra produced ?

light has a mixture of wavelengths the constructive interference occurs at different angles for each wavelength .A set of coloured line spectra is produced rather just a set of bright fringes.  


Emission Spectra

The light is emitted when the electron in atoms are excited by heating or by an electric discharge is characteristic of the electronic structure of the elements present Flame test can be used to identify elements such as gas


Double slight when it arrived ?

When we have a double slit the waves have arrived at the same difference to waves which look like a issol


What about dark fringes ?

Whereas in between where's there's a dark fringe , the path difference is half a wavelength , where the waves arrive 180 out of phase causing a destructive interference in which they cancel each other out causing a dark fringe .At this point no light is reflected


What order do we get bright fringes ?

Bright fringe we get is the Oth order and so on .


what happens tho the path difference between waves adjacent sources wokre out to be whole number ?

then the displacements due to waves from all separate sources will be in phase .They add together constructively to give a bright spot of high intensity of radiation at the point .The same effect can be cleary demonstrates with water ripples .





Grafting in reflection mode

look at the part of the wave energy is bounced back off the grafting surface because the grating lines spaces they pattern is produces


Advantage of reflection mode

You don't have to focus on the transparency of the grafting .It doesn't matter whether the waves are transmitted or absorbed but its the reflectivity of the grafting surfaces that counts or giving strong signal .


Discuss how path difference and phase difference contributes to the production of spectra by diffraction grating .

The path difference between the waves coming from adjacent lines depend on the angle through which the light is scattered .

If the path difference is a whole number of wavelength then the waves will be in phase and interfere constructively giving bright lines

In between when the phase difference is near 180 degrees destructive interference causes darkness.