The equation,

<img src='./qimages/10487-1a.jpg'>

represents a wave where length is expressed in em, and t in seconds.

Is the wave progressive or stationary

What is its amplitude and angular velocity?

Define beats.

What will be the pressure due to plane progressive sound waves in air at a point where the particle velocity is 1 mm/s along forward direction Given the velocity of sound in air =340 m/s and y for air =1·4.

What is the difference between interference and diffraction of light?

Give the relation between group velocity and wave velocity.

Calculate the rest energy of an electron in Joules and in electron volts.

At what speed is a particle moving, if the mass is equal to three times the rest mass

Calculate the radius and energy of the electron in the nth orbit in hydrogen from the following data:

e 1·6 x 10^-19 Coulomb, m 9·1 x 10^-31 kg;
h 6·6 x 10^-34 Joule-second;
€o 8·85 x 10^-12 farad/m and c 3 x 10^8 m/s.

Define free, forced and damped oscillations.

Explain Pauli's exclusion principle.

Define spontaneous emission and population inversion.

When a thin sheet of transparent material of thickness 6·3 x cm is introduced in the path of one of the interfering beams, the central fringe is shifted to the 6th bright fringe. If 5460 find the refractive index of the sheet.

Define critical potential, excitation potential and ionisation potential of a hydrogen atom.

Calculate the wavelength associated with a particle of mass 1g moving with a velocity of 2000 m/s.

A microscope, using photons, is employed to locate an electron in an atom to within a distance of 0·2 A. What is the uncertainty in the momentum of the electron located in this way?

2. A horizontal coiled spring is found to be stretched by 0·10 m from its equilibrium position, when a force of 4 N acts on it. Then a body of mass 1·6 kg is attached to one end of the spring and is pulled by 0·12 m along a horizontal frictionless table from equilibrium position. The body is then released and executes SHM. Find

The force constant of the spring

The force exerted by the spring on 1·6 kg mass just before it is released

Period of oscillation

Amplitude

The velocity, acceleration, KE and PE of the body when it has moved half away from its initial position towards the centre.


3. Define Lissajous figure and discuss the necessary theory of superposition of two rectangular waves of equal frequencies but different amplitudes.

4. Define the following terms:

Amplitude

Phase

Path difference

Stationary wave

Progressive wave

5. State the basic postulates of Einstein's Special Theory of Relativity and also discuss length contraction and time dilation.

6. Derive Galilean transformation equations.

7. Explain, with its principle, the construction and working of He-Ne laser.

8. Using the physical constants given below, calculate the following for a hydrogen atom:

Velocity of an electron in ground state

Radius of Bohr's orbit in ground state

Time taken by an electron to traverse the first Bohr orbit

Rydberg's constant Electronic charge e =1·6 x 10^-19 Coulomb Electronic mass m 9.1 x 10^-31 kg Planck's constant h =6.6 x 10^-34 Joule-sec Speed of light c x 10^8 m/s Permitivity of free space €o =8.86 x 10^-12

9. Explain Fraunhofer diffraction through a single slit with a neat diagram.