# Gujarat PSC: 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

P0/2ppg

- 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