Cork Institute of Technology
Bachelor of Engineering (Honours) in Structural Engineering - Stage 1
(Bachelor of Engineering in Structural Engineering – Stage 1)
(NFQ Level 8)
Summer 2005
Physics
(Time: 3 Hours)
Answer FIVE questions only.
Show ALL working to gain full marks.
Assume: g = 10.0 ms-2
Examiners: Prof. P. O Donoghue
Mr. T. Corcoran
Dr. M. E. Woods
Q1. (a) State: (i) Archimedes Principle; (ii) The Principle of Flotation [5 marks]
(b) A fisherman of mass m makes a raft of mass M = 500 kg. The raft floats a depth of
d
1 = 6.0 cm when initially placed in the water by itself. When the fisherman steps on the
raft it sinks a depth of 8.0 cm. What is the mass of the fisherman? [7 marks]
(c) A submarine is at a depth H below the surface of the sea of density 1050 kg m-3. The total
surface area of the submarine is 50 m2. The submarine experiences a pressure of 250 kPa.
Calculate:
(i) Depth H;
(ii) The force F exerted on the hull by the sea. [8 marks]
Q2. (a) Define the following properties of waves:
(i) Interference; (ii) Diffraction. [4 marks]
(b) Illustrate diffraction by showing the passage of a plane wave of wavelength λ through an
aperture of width d, for which the aperture width is:
(i) much larger than the wavelength [d >> λ];
(ii) the same as the wavelength [d = λ]. [4 marks]
(c) A monochromatic plane light wave is is incident on Young’s slits. Explain how bright
fringes are obtained. Derive the diffraction equation for bright fringes. [6 marks]
(d) Yellow light of wavelength 600 nm falls on a diffraction grating with 500 lines per mm.
Determine the diffraction angle of the first order diffraction line. State ONE difference in
the appearance of the fringes if Young’s slits were used instead of the diffraction grating.
[6 marks]
