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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 3 Examinations 2007/
Module Title: Engineering Physics
Module Code: PHYS 6003
School: School of Mechanical and Process Engineering
Programme Title: Bachelor of Engineering (Honours) in Mechanical Engineering - 1
Bachelor of Engineering (Honours) in Electronic Engineering – Year 1
Programme Code: EMECH_8_Y EELXE_8_Y
External Examiner(s): Mr. P. Clarke, Prof. M. Gilchrist Internal Examiner(s): Mr. G.M. Croke
Instructions: Answer FOUR questions.
Duration: 2 HOURS
Sitting: Autumn 2008
Requirements for this examination:
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator.
Physical Constants Charge on electron ( e ) 1.60x10 -19^ C Speed of light in a vacuum ( c ) 3.00x10^8 m s -
Avogadro’s No ( ΝΑ) 6.02x10^23 mol -1^ Planck’s Constant ( h )^ 6.63x10-34^ Js Rest mass of electron ( m (^) e ) 9.11x10-31^ kg
Q1 (a)^ Two lenses are placed a distance of 60cm apart. The first lens is bi-convex with a focal length of 20cm. The second lens is also bi-convex and has a focal length of 25cm. An object of height 10cm is placed 40cm to the left of the first lens. Use a ray tracing technique to estimate where the images are formed, their type and orientation and the overall magnification of the system of lenses. (15 Marks)
(b) State the thin lens equation and use it to confirm the results obtained in (a) above. (10 Marks)
Q2 (a) Describe clearly the principle underlying the operation of a fibre optic cable and outline the construction of such a cable. (13 Marks) (b) Derive an expression for the maximum angle of incidence on a step-index fibre to ensure propagation down the fibre. A step-index fibre of numerical aperture 0.10 uses a cladding of refractive index 1.492. Calculate the refractive index of the core and the acceptance angle of the fibre. (12 Marks)
