This document contains exam questions for a biomedical engineering midterm on analytical instrumentation. It includes questions on: - Plank's theory of radiation and photon interactions with atoms. - Absorption, emission, and fluorescence spectra of hydrogen gas irradiated with UV light. - Comparing mirrors/lenses and prisms/gratings as optical components. - Calculating transmitted wavelength through an interference filter and emissive power from a blackbody. - Describing the optical design of a Rowland circle grating monochromator and its advantages/limitations. - Calculating maximum photoelectron speed, stopping potential, minimum radiation intensity, and photon rate for a cesium photocell

1. Cairo University 3rd year Biomedical Eng. Nov. 2006
Faculty of Eng. Mid Term Exam-Analytical Instrumentation Time : 90 Min
Answer as many as you can: Full mark = 30 Degrees
(1a) State Plank's theory for the particle nature of radiation, then show using diagrams the possible
interactions that may be occur when a photon of energy E=hν is incident on an atom. [5 Degrees]
(1-b) Hydrogen gas has ionization potential 13.6 volt is irradiated by an U.V. beam of wavelength band
10095 ≤≤ λ nm. Find the corresponding characteristic wavelengths of the absorption, emission
and fluorescence spectra and the energy levels of the gas. Show your answer by energy `level
diagram. [7 Degrees]
(2-a)Compare between :
(i) Mirrors and lenses as collimating and focusing means.
(ii) Prisms and diffraction gratings as fanning means.
(iii) Color glass filters and Interference filters as wavelength selection means.
Use clear sketches in all cases. [5 Degrees]
(2-b)Find the following:
(i)The transmitted wavelength from an Interference filter of thickness 200 nm, if its material refractive
index is n=2.38 in case of normal incidence.
(ii) 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.
(iii) The number of slits per cm (N) for a gating, if the diffraction angle of the red color (647 nm)
incident on it, is found to be α=15o
in the first order. [7 Degrees]
(3-a) Draw a clear diagram showing the optical design of the Rowland concave grating monochromator,
showing its advantages and sufferings and show how they can be corrected. [5 Degrees]
(3-b) For a photoelectric cell with cathode made of Cesium ( work function is 1.35 eV) is illuminated with
light of wavelength 400 nm. Find:
i-The maximum speed of the emitted photoelectrons at the cesium’s surface.
ii-The stopping potential.
If the minimum output anode current required for detection is 10-2
Amp,Find:
vi- The minimum intensity incident radiation.
v- The rate of incident photons in this case.
(7 degrees)
Electron charge = -1.6 x 10-19
C
Speed of light in vacuum = 3 x 108
m/sec ,
Planck’s constant h = 6.63 x 10-34
Joule.sec
Stafan's constant σ = 5.6 x 10-8
w m-2 o
k-4