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IIT JEE Physics MCQ Set 7 | Waves & Thermodynamics

IIT JEE SET 7 WAVES & THERMODYNAMICS

Physics Practice Paper Set 7

Waves · Sound · Thermodynamics · Kinetic Theory

Questions: 30 Marks per correct: +4 Negative marking: None Max Score: 120 Suggested Time: 60 min

📋 Instructions

  • Each question carries 4 marks. There is NO negative marking in this set.
  • Select one option per question. Only your last selected option will be recorded.
  • Click “Submit Paper” after attempting all questions.
  • Unattempted questions will be counted as wrong (0 marks).
  • Results with detailed explanations appear immediately after submission.
Question 01
A string of length \(L\) is fixed at both ends and vibrates in its 3rd harmonic. The ratio of the wavelength of the standing wave to the length of the string is:
Question 02
A train moving at 30 m/s emits a whistle of frequency 600 Hz. If the speed of sound is 330 m/s, the apparent frequency heard by a stationary observer standing behind the train is:
Question 03
Two sound waves of frequencies 256 Hz and 260 Hz superpose. The number of beats heard per second is:
Question 04
An open organ pipe of length 0.5 m resonates at its fundamental frequency. If speed of sound is 340 m/s, the fundamental frequency is:
Question 05
The intensity of sound at a point is \(10^{-8}\) W/m². If the threshold intensity is \(10^{-12}\) W/m², the sound level in decibels is:
Question 06
A closed organ pipe of length \(L\) produces its first overtone at the same frequency as the fundamental of an open pipe of length \(L’\). The ratio \(L : L’\) is:
Question 07
A wave is represented by \(y = 5\sin(2\pi t – \frac{\pi x}{3})\) (SI units). The phase velocity of the wave is:
Question 08
In a stationary wave, the distance between two consecutive nodes is 0.3 m. The wavelength of the wave is:
Question 09
The speed of sound in a gas at 27°C is \(v\). At what temperature (in °C) will the speed be \(2v\)?
Question 10
The tension in a string is quadrupled. The speed of the transverse wave in it will become:
Question 11
For an ideal gas undergoing an isothermal process, which of the following remains constant?
Question 12
One mole of a monatomic ideal gas is taken through an adiabatic process. The ratio \(\gamma = C_p / C_v\) for a monatomic ideal gas is:
Question 13
The work done by a gas in an isothermal expansion from volume \(V_1\) to \(V_2\) at temperature \(T\) is:
Question 14
A Carnot engine operates between temperatures 500 K and 300 K. Its efficiency is:
Question 15
According to the equipartition theorem, the internal energy of one mole of a diatomic gas (rigid) at temperature \(T\) is:
Question 16
The rms speed of oxygen molecules at 27°C is approximately (M = 32 g/mol, R = 8.314 J/mol·K):
Question 17
During an adiabatic process, the relation between pressure and volume is \(PV^\gamma = \text{const}\). For this process, the work done by the gas is:
Question 18
A gas absorbs 600 J of heat and does 250 J of work. The change in internal energy of the gas is:
Question 19
The mean free path of a gas molecule is inversely proportional to:
Question 20
In a \(p\text{-}V\) diagram, an isochoric process is represented by:
Question 21
Two waves \(y_1 = A\sin(\omega t)\) and \(y_2 = A\sin(\omega t + \phi)\) are superposed. For completely destructive interference, \(\phi\) must be:
Question 22
The velocity of sound in air at STP is about 332 m/s. At 100°C (373 K), the speed will be approximately:
Question 23
Which of the following processes is represented by \(\Delta U = 0\)?
Question 24
For a diatomic ideal gas, the ratio of the slope of the adiabatic curve to the slope of the isothermal curve (at the same point on the \(p\text{-}V\) diagram) is:
Question 25
The Doppler effect is NOT observed when:
Question 26
The number of degrees of freedom for a rigid diatomic molecule is:
Question 27
A string vibrates in 4 loops when 36 g is suspended. To make it vibrate in 6 loops, the mass suspended should be:
Question 28
For an ideal gas, at constant pressure, the graph of volume vs absolute temperature is:
Question 29
If the pressure of a gas is doubled at constant volume, the rms speed of the gas molecules becomes:
Question 30
The second law of thermodynamics implies that:
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