# Punjab PSC Exam: Physics MCQs (Practice_Test 13 of 35)

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- Which of the above figures represent damped simple harmonic motion. Select the correct answer using the codes given below:
- Fig 1 alone
- Fig 2 alone
- Fig 4alone
- Fig 3 and 4

- A railway engine passes by the platform at a speed of 36 km/hr blowing Its whistle having a frequency of 660 Hz. The different in the frequencies of the whistle heard by a person standing on the platform as the engine goes past the person is equal to
- zero
- 20 Hz
- 40 Hz
- 60 Hz

- An open pipe of length 33 cm resonates to a frequency of 1000 Hz. The mode of vibration is
- fundamental
- the first harmonic
- the second harmonic
- file fourth ham1onic

- In the case of forced simple harmonic vibrations, the body generally vibrates with
- Its natural frequency of vibration and its amplitude is small
- its natural frequency of vibration but its amplitude is large
- the frequency of the external force with a small amplitude
- the frequency of the external force with a large amplitude

- A string 1 m long is drawn by a 300 Hz vibrator attached to its end. The siring vibrates in three segments. The speed of transverse waves in the string is equal to
- 100 m/s
- 200 m/s
- 300 m/s
- 400 m/s

- A string vibrates in 5 segments to a frequency of 480 Hz. The frequency that will cause it to vibrate in 2 segments will be
- 96 Hz
- 192 Hz
- 1200 Hz
- 2400 Hz

- Given that a sound wave is passing through a gaseous medium of density p, pressure p and having specific heat ratio g, and if P0 be the amplitude of the pressure variation of the sound wave, then match List I with List II and select the correct answer using the codes given below:
List-I (Properly) List-II (Expression) - Velocity of sound wave
- Intensity of sound wave
- Acoustic impedance of the medium
- Bulk modulus for an adiabatic change

- p pg
- gp
- gp/p
- P ppg

- A
- B
- C
- D

- 3
- 4
- 2
- 1

- 4
- 1
- 3
- 2

- 3
- 4
- 1
- 2

- 2
- 3
- 1
- 4

- If the differential equation given by d2y/dt2 + 2 k dy/dt + w2y = F0 sin pt describes the oscillatory motion of body in a dissipative medium under the influence of a periodic force, then the state of maximum amplitude of the oscillation is measure of
- free vibration
- damped vibration
- forced vibration
- resonance

- A lens system made up of two thin lenses 1 and 2 of focal lengths + f and-f respectively are separated by a distance + f. Under paraxial approximation, the system mabix for a ray entering from the left of lens l and leaving to the right of lens 2 is given by
- 1
- 2
- 3
- 4

- Which of the following combination (s) will reduce spherical aberration of a convergent lens to practically zero?
- Convergent lens
- Divergent lens
- Plane mirror
- Spherical mirror

Select the correct answer using the codes given below:

- 1 and 3
- 2 alone
- 3 and 4
- 4 alone

- Two convex lenses made of flint glass and of focal lengths 20 cm and 40 cm will become achromatic if the distance between them is
- 10 cm
- 20 cm
- 30cm
- 60cm

- The ‘f’ number of a photographic camera with aperture D and focal length F is
- (F/D)
- (D/F)
- (FD)
- (FD) 1

- Which one of the following sets of waves is coherent?
- With light of wavelength 490 nm in a Newton՚s rings experiment, the radius of the nth bright ring is R With light of wave-length 640 nm, in the same set up, the corresponding radius will be
- 8 Rn/7
- 64 Rn/49
- Rn
- 7Rn/8

- The intensity of light emerging from one slit in a Young՚s double-slit interference set up is four times that of the other. The ratio of maximum intensity to minimum intensity in the fringe pattern is
- 4: 1
- 2: 1
- 9: 1
- 3: 1