Q- A collimated gamma ray beam consists of equal numbers of 0.1 MeV and 1.0 MeV photons. If the beam enters a 15 cm thick concrete shield, what is the relative portion of 1 MeV photons to 0.1 MeV photons in the emergent beam?

## . July 2017

### Electromagnetic waves

Q- The intensity of sunlight striking the earth's upper atmosphere (called the solar constant) is 1.35 kW/m^{2}.

(a) Find *E*_{rms} and *B*_{rms} due to the sun at the upper atmosphere of the earth.

(b) Find the average power output of the sun

(c) Find the intensity at the surface of the sun.

(d) Find th…

### Friction and Projectile

Q- A block slides 6 feet down the incline of an escalator and then it slides for 2 feet along the level portion until if flies off. If the level portion of the escalator is 3 feet above the floor, determine how far from the base of the escalator the block will strike the floor. Assume that the coeff…

### Heat and Thermodynamics

Q- A spherical tank contains 1 mole of helium gas at 10 bar and 300 K. The gas is slowly released to the atmosphere in such a way the remaining gas is maintained at constant total energy U. Heating or cooling may be used to keep U constant during the venting. Helium behaves as an ideal gas with a co…

### Electrostatics: Field in Cavity

Q. A sphere of radius r_{0} carries a volume charge density ρ_{E}. A spherical cavity of radius r_{0}/2 is then scooped out and left empty, as shown.

(a) What is the magnitude and direction of the electric field at point A?

(b) What is the direction and magnitude of the electric field at point B? Poin…

### Fluid Dynamics

Q- A hypodermic syringe is attached to a needle that has an inner radius of 0.305 mm and a length of 3.00 cm. The needle is field with a solution of viscosity 2.01*10^{-3} Pa^{.}s. It is injected in to a vein at a gauge pressure of 16.6 mm of Hg.

(a) What must the pressure of the fluid in the syringe be …

### Alternating Current: Series Resonance

The cut-off frequencies of a series resonant circuit are 5400 Hz and 6000 Hz.

(a) Find the Bandwidth of the circuit.

(b) If quality factor Q = 9.5, find the resonant frequency of the circuit.

(c) If the resistance of the circuit is 2 Ω, find the value of reactance X_{L} and X_{C} at resonance…

### Sound Waves: Interference

Q- A riverside warehouse has two open doors and its walls are lined with sound absorbing material. A boat on the river sounds its horn. To a person A on the perpendicular bisector of the doors, at a distance 150 m from the doors, sound is loud and clear while to a person B, 30 m sideways from A, the…

### Ray Optics: Total Internal Reflection

Q- A layer of unknown liquid is held on a flint glass slab with an index of refraction 1.65. A ray of light is falling on the glass liquid interface from below and the critical angle for the interface is 53^{0}.

(a) What is the refractive index of the unknown liquid?

(b) If the liquid is removed, wha…

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