Dear tutor: I need help with part B of my lab indicated below

Experiment 7

SPECTROSCOPY

In most branches of science, scientists can take a sample of whatever they're studying for closer examination in the laboratory. Astronomers, however, work with the handicap of being separated from the objects we study by enormous distances.

Given that we are mostly restricted to observing the light that arrives here from distant objects, astronomers make as much use as possible from this light, using every method available.

One such method is spectroscopy. Spectroscopy is a technique that breaks down light into its constituent parts. The "parts" are the light at different wavelengths (different colours).

A spectrometer is a device that breaks down incoming light into these separate colours. (In this sense, there are "spectrometers" in nature, such as the rain droplets that break down sunlight into a rainbow.) At an observatory, spectrometers record and measure the spectrum of the light that is fed into them from the telescopes. By studying the spectrum of a star, a galaxy, or any celestial object, we can gain much valuable information about the object.

For one, the spectrum of a moving object can be used to measure its speed using the Doppler Effect (redshift). This uses the same principle that allows the police to measure the speed of a moving car.

Another application of spectroscopy is to determine the chemical composition of an object. This is possible because every element and every molecule emits light at specific wavelengths in a way that is unique to that substance. For example, if you see light from a star appearing at the wavelengths for Oxygen, then you can conclude that this star contains Oxygen.

There are many types of spectrometers, but the two main types used for visible wavelengths are the grating spectrometer and the prism spectrometer.

A prism uses the fact that light of different wavelengths will refract ("bend") by slightly different angles when they pass through a glass wedge (the prism).

A diffraction grating is a transparent material that has very fine lines etched into it at regular spacings. Some of the light that passes through a grating also changes direction in a way that depends on wavelength, allowing the diffraction grating to also spread out light into its different colours.

Part B: Identifying a Gas with an Emission Spectra

In this part of the experiment, you will use the simulation for the grating spectrometer to find the wavelengths of light emitted by a "mystery" gas. By comparing the measured wavelengths and observed colours with known patterns for a selection of gases, you will identify your unknown gas.

Objective

To (a) measure the wavelengths of the spectral lines emitted by an unknown gas by means of a grating spectrometer simulation, and (b) identify the unknown gas.

Theory

Remember that a diffraction grating has a series of very finely spaced lines etched on it. These are so closely spaced (several hundred lines per millimetre) that you can't see them with the naked eye.

\fspectrum tube power supply spectrum tube telescope collimator telescope focus knob eyepiece prism prism clamp spectrometer slit width adjustment screw telescope lock collimator focus knob telescope fine adjust knob spectrometer table lock spectrometer table\fMove the telescope until the crosshairs are exactly on top What the eye sees: Angle 41.19 of a spectral line Read the angle here\fFacts About: Hydrogen Hydrogen Helium Nitrogen Oxygen Neon Argon Krypton Xenon Mercury 41071 mm andram 0145 mm