## Old Question Paper 2009 – Physics

Pokhara University | Level: Bachelor | Year: 2009

Programme: BE (Bachelor of Engineering)

Full Marks: 100 | Pass Marks: 45 | Time: 3 hrs

Candidates are required to give their answers in their own words as far as practicable. The figures in the margin indicate full marks.

**Attempt all the questions.**

- a. Derive and expression for the time period and radius of gyration of a compound pendulum and show that centre of oscillation and centre of suspension are interchangeable. [9]

b. Calculate the wave length, frequency, speed of the wave and maximum particle velocity in the wave represented by y = 20 sinπ (2t – 0.05x). The values of x and y are in centimeters. [6] - a. What are beats? Show that beat frequency is given by the difference of frequencies of two waves. [9]

b. The objects glass of telescope is an achromatic of focal length 90 cm. If the magnitudes of the dispersive powers of the two lenses are 0.024 and 0.036, calculate their focal lengths. [6] - a. What are coherent sources? Discuss analytical treatment of interference and energy distribution in young’s double slit experiment. [9]

b. What is the highest order speed which may be seen with monochromatic light of wave length 6000 Aᵒ by means of a diffracting grating with 5000 lines/cm. [6] - a. Define capacitance of a capacitor. Also, derive and expression for the energy stored by a capacitor. [9]

b. A rectangular carbon block has dimensions 1.0cm X 1.0cm X 50 cm. What is the resistance measured: [6]

i) Between the two squares ends.

ii) between two opposing rectangular faces. - a. Explain Biot and Savart law with its one application. [9]

b. A circular loop of wire 5 cm of radius carries a current of 100 amps. What is the energy density at the centre of the loop? [6]