Question

1) what is a diffraction grating

2) why do we use "discharge tube" to perform the experiment instead of a light bulb

3)If "d " is the grating constant (spacing in between two slits on a grating), hoe can we obtain the ruling (number of grooves per meter) "D"?

4) Define " order of diffraction" and illustrate it using a drawing

Answer 1

(1) What is a diffraction grating?

A diffraction grating is the tool of choice for separating the colors in an incident light. There are multiple orders of the peaks which associated with the interference of light through the multiple slits. Diffraction gratings work for transmission of light and a reflection of light. They are commonly used for spectroscopic dispersion and analysis of light.

(2) Why do we use "discharge tube" to perform the experiment instead of a light bulb.

Basically, discharge tube is a family of artificial light sources that generate light by sending an electric discharge through an ionized gas & a plasma. Typically, such tube use a noble gas (like argon, neon, krypton and xenon) or a mixture of these gases. In an experiment, some of the electrons are forced to leave the atoms of a gas which near the anode by an electric field applied between the two electrodes, leaving these atoms positively ionized.

As Compared to a light bulb, discharge tube offer higher efficiency. Some gas-discharge tube also have a perceivable start-up time to achieve their full light output. Due to their greater efficiency, gas-discharge tube were preferred over a light bulbs in many lighting applications.

(3) If "d" is the grating constant (spacing in between two slits on a grating), how can we obtain the ruling (number of grooves per meter) "D"?

An expression for grating which is given below as :

d sin = m

which governs the angles of diffraction from a grating of groove spacing 'd'.

Here, m is the diffraction order which is an integer.

For a particular wavelength, all values of 'm' for which | m / d | < 2 which correspond to physically realizable diffraction orders.

Conveniently, an above expression can be written as :

d sin = D m

where, D = 1 / d = number of grooves per meter