GTU Exam Papers Solved

GTU Exam Paper Solved (Physics):

Subject code: 110011, Subject Name: Physics
Date: 18 / 03 /2009

Q:1 Attempt all the question.
1 Classify the sound waves based on frequency.
Based upon the frequency of sound waves it ca be define into three part
[a] Audible waves : 20 Hz to 20 KHz
[b] Infrasonic waves : below 20 Hz
[c] Ultrasonic waves : above 20 KHz
2 Define Reverberation time.
Reverberation time is defined as the time gap between initial direct note and reflected note at a
minimum audible level.
3 Define Ultrasonic waves.
The sound waves of frequency above 20kHz are called ultrasonic waves.
4 What is magnetostriction method?
Magnetostriction method is used to generate ultrasonic waves up to 3000 KHz using
magnetostriction effect.
5 What is SONAR?
The full form of Sound Navigation and Ranging. It is based on the principle of echo sounding.
6 What are lattice parameters?
There are six parameters : a, b, c,  , .
7 What is LASER?
Light Amplification by stimulated emission of radiation. It is based on principle of echo sounding.
8 Define fiber optic system?
Fiber optic system is a communication system which uses optical fibers and light signal to carry
information signal.
9 What are conduction electrons?
The electrons in conduction band are called free or conduction electrons.
10 Classify the solids based in band theory.
Solids are classified into (1) conductor (2) semiconductor (3) Insulator.
11 What is holography?
Holography is techniques that allow the light scattered from an object to be recorded and later
reconstructed so that it appears as if the object is in same position relative to recording medium as
it was when recorded.
12 Define superconductor?
Superconductivity is defined as state of zero resistivity and perfect conduction of current through
it.
13 What are Nanomaterials?
A nanomaterial is made up by grains that are about 100 nm in diameter and contains less than a
few ten thousand of atoms.
14 Mention the names of the various NDT methods.
1 liquid penetrate-dye penetrate inspection
2 X-ray radiography
3 Ultrasonic inspection method
4 Magnetic particle inspection
5 Visual inspections.
6 Sonic inspections.

 

Discuss the various factors affecting the acoustics of buildings and give their
Remedies
Reverberation is one of the important factors that affect the acoustics of a building. Besides reverberation
there are other factors like loudness, focusing, echelon effect, extraneous noise and resonance.
Loudness:-
Suppose 1000 persons can hear the speech of a person in an auditorium, but there will not be any uniform
sound distribution. So to ensure uniform distribution of sound intensity in the hall electrically amplified
loudspeakers are used. These speakers are kept in different places in the auditorium and are kept at a higher
than the speaker’s head. Amplifiers shall make the low frequency tones more prominent and hence the
amplification has to be kept low.
Focusing
The presence of cylindrical or spherical surface on the wall or the ceiling gives rise to undesirable focusing.
In hall, the observer receives sound waves from the speaker along the direct path and the observer also
receives the sound waves after reflection from the ceiling.
Echelon effect:-
If there is regular structure similar to a flight of stairs or asset of railways in the hall, the sound produced in
front of such a structure may produce a musical note due to regular successive echoes of sound reaching the
observer. Such an effect is called echelon effect. If the frequency of this note is within the audible range, the
listeners will hear only this note prominently. To avoid echelon effect, the staircase must have to be covered
with carpets.
Extraneous noise:-

The extraneous noise may be due to the sound received form outside the auditorium and the sound produced
by fans inside the auditorium. The external sound cannot be completely eliminated but can be minimized by
using double or triple windows and doors. Proper attention must be given to maximum permissible speed of
time and the rate of air circulation in the room. The air conditioning pipes should be covered with corks and
insulated acoustically forms the main building.
Resonance:-
The acoustics of a building may also be affected by resonance. So if the hall is of large size the resonance
frequency is much below the audible frequency limit and harmful effect due to resonance will not be
affected
Reverberation time: -
the auditorium must be designed in such a way that it could have the optimum reverberation time.
In an auditorium reverberation time can also be maintained by eliminating unwanted echoes, focusing
effects of curved surfaces, flatter echoes etc., Echoes, etc.
Sound absorption:-
Sound absorption is a process in which sound energy is converted partly into heat and partly in to
mechanical vibrations of the material. Carpets, suspended space absorbers and interchangeable absorption
panels in rooms and buildings can absorb unwanted sound.

 

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