Bioanalysis Midterm nov.2010 3rd-biom

1. Cairo University 3rd year Biomedical Eng. Nov. 2010
Faculty of Eng. Mid Term Exam-Analytical Instrumentation Time : 60 Min
Answer as many as you can: Full mark = 30 Marks
(1-a) Draw a clear diagram of the optical design of the double-grating monochromator and
label its different components. State the advantages of this monochromator and mention
two sources of UV radiation that may be used. ( 6 Marks)

2. (1b) State the advantages and disadvantages of each of the following pairs: (6 Marks)
i- Mirrors and lenses as collimating and focusing elements.
ii- Prisms and diffraction gratings as fanning elements.

3. (2-a) Show in a clear diagram the different parts of a Fluorescent Lamp and label its
different components. State the type and range of its characteristic spectrum. State how the
same lamp can be altered so that it can be used as a source of UV radiation.
( 6 Marks)

4. (2-b) Find the following :
i- The emissive power per unit area from a black body if it is found that the wavelength at
which the maximum monochromatic emissivity occurs is 1100 nm. (Stefan's constant
σ = 5.6 x 10-8
watt m-2 o
k-4
and Wien’s constant = 2.93 x 10-3
m. 0
K ) ( 3 Marks)
ii- The number of slits per cm for a diffraction grating to get a Dispersion D = dλ/dx = 50
nm/mm on a screen that is 40 cm away from the grating. ( 3 Marks)

5. (3) A certain Hydrogen-like gas is found to be ionized when it absorbs radiation of
wavelength 22.83 nm. Find the characteristic wavelengths of the resulting: (a) Absorption,
(b) Emission, and (c) Fluorescence spectra if this gas is excited by a potential difference of
51.4 volts. Illustrate your answer using energy level diagrams. ( Electron charge = -1.6 x 10-19
coulomb, speed of light in vacuum = 3 x 108
m/sec, and Planck’s constant = 6.624 x 10-34
Joule sec ) ( 12 Marks)