# Competitive Exams: Physics MCQs (Practice-Test 35 of 35)

1. A thin plate of mica of thickness 0.15 mm (refractive index 1.5977 and 1.5601 along the gamma and alpha axes respectively) is oriented 45'between the crossed polarizer and analysed through an analyser. The colour of the specimen will be

1. blue

2. green

3. yellow

4. red

2. If the scattering intensity of a liquid is 6 units at a wavelength of 500 nm, then the scattering intensity at a wavelength of 400 nm will be approximately

1. 3

2. 6

3. 12

4. 15

3. When excited by a light of wavelength 4358 A, a transparent substance produces a Stokes Raman frequency shift of 458 cm-1. The wavelength of the antistokes line is

1. 4058

2. 4274

3. 4448

4. 4548

4. Carbon dioxide shows a Raman line at 1080 cm-1. Consider the following statements in this regard?

1. The corresponding infrared absorption will be found at 1080 cm-1.

2. The corresponding infrared absorption band will be absent.

3. CO2 is a linear and symmetric molecule.

Of these statements

1. 1 and 3 are correct

2. 2 and 3 are correct

3. 2 alone is correct

4. 3 alone is correct

5. Match List I (Lasers) with List II (Methods of population inversion to produce laser action) and select the correct answer

 List-I List-II He-Neon Argon ion Semiconductor Carbon dioxide Molecular collision Electric discharge Direct conversion Electron impact
• A
• B
• C
• D
• 2
• 4
• 3
• 1
• 2
• 4
• 1
• 3
• 4
• 2
• 3
• 1
• 4
• 2
• 1
• 3
6. When two tuning forks A and B are sounded together 6 beats per second are produced. The frequency of B is 320 Hz. If some wax is added to A and again sounded with B, again 6 beats per second are produced. The frequency of A is

1. 326 Hz

2. 332 Hz

3. 314 Hz

4. 308 Hz

7. Two railway engines re moving on parallel tracks in opposite directions, each with a speed of 72 kmph. The whistle of one engine blows a note of frequency 589 Hz. Given that the velocity of sound is 330 m/s, the frequency which will be heard by the driver of the other engine, just before crossing is

1. 919 Hz

2. 665 Hz

3. 589 Hz

4. 259 Hz

8. The four curves shown in the given figure represent the variation of amplitude (A) with driving frequency (W) for different values of damping constant. The curare which represent zero damping is the curve label

1. W

2. X

3. Y

4. Z

9. A damped simple harmonic oscillator of frequency f1 is constantly driven by an external periodic force of frequency f2. At the steady state, the oscillator frequency will be

1. f1

2. f2

3. f1 − f2

4. (f1 + f2)/2

10. An open organ pipe has a fundamental frequency of 300 Hz. The first overtone of this organ pipe is the same as the first overtone of a closed organ pipe. The length of the closed organ pipe is (assume velocity of sound in air as 330 m/s)

1. 0.41 m

2. 0.78 m

3. 0.82 m

4. 0.90 m

11. Which one of the following is the expression for the second overtone of an organ pipe of length ‘l’ (u = velocity of sound)?

1. u = 3u/2l

2. u = u/l

3. u = 2u/l

4. u = 3u/5l

12. The velocity of longitudinal waves in quartz is 5.46 × 103 m/s. If the thickness of the quartz crystal is 1mm, then the frequency of the ultrasonic wave generated by it is

1. 2.73 kHz

2. 5.46 kHz

3. 2.73 MHz

4. 5.46 MHz

13. An ultrasonic sound pulse is sent vertically down the ocean waters and the echo is reserved 3 seconds later. The depth of the ocean at that place is approximately

1. 1.1 kilometers

2. 2.2 kilometers

3. 3.3 kilometers

4. 4.4 kilometers