Equation of the wave is given by y = 0.4 sin(314t - 3.14x), where x and y are in meter and t is in second. The speed of the wave is :

1.  50 m/s

2.  100 m/s

3.  314 m/s

4.  3.14 m/s

When a wave is reflected from a denser medium the change in phase is :

1.  0

2.  $\mathrm{\pi }$

3.  $2\mathrm{\pi }$

4.  $3\mathrm{\pi }$

The equation of a wave pulse travelling along x-axis is given by $y=\frac{30}{2+{\left(x-20t\right)}^2}$, x and y are in meters and t is in seconds. The amplitude of the wave pulse is 

1.  5 m

2.  20 m

3.  15 m

4.  30 m

The sound intensity level at a point 10 m away from a point source is 20dB, then the sound level at a distance 1m from the same source would be

(1) 40 dB

(2) 30 dB

(3) 200 dB

(4) 100 dB

In the phenomenon of interference of sound by two coherent sources if difference of intensity at maxima to intensity at minima is 20dB, then the ratio of intensities of the two sources is

1.  $\frac{121}{81}$

2.  $\frac{11}{9}$

3.  $\frac{101}{99}$

4.  $\frac{10}{1}$

When a sound wave travels from one medium to another, the quantity that remains unchanged is :

1.  speed

2.  amplitude

3.  frequency

4.  wavelength

Two waves are represented by the equations ${\mathrm{y}}_1=\mathrm{a} \sin (\mathrm{\omega t}+\mathrm{kx}+0.57)\mathrm{m}$ and ${\mathrm{y}}_2=\mathrm{a} \cos (\mathrm{\omega t}+\mathrm{kx})\mathrm{m}$, where x is in metre and t in second. The phase difference between them is?

(1) 1.25 rad

(2) 1.57 rad

(3) 0.57 rad

(4) 1.0 rad

Sound waves travel at 350 m/s through a warm 

air and at 3500 m/s through brass. The wavelength

of a 700 Hz acoustic wave as it enters brass from 

warm air :

(1) increases by factor 20

(2) increases by factor 10

(3) decreases by factor 20

(4) decreases by factor 10

Two particles are oscillating along two close parallel straight lines side by side, with the same frequency and amplitudes. They pass each other, moving in opposite directions when their displacement is half of the amplitude. The mean positions of the two particles lie on a straight line perpendicular to the paths of the two particles. The phase difference is :

(1)zero                                 

(2)$\frac{2\mathrm{\pi }}{3}$

(3)$\mathrm{\pi }$                                     

(4)$\frac{\mathrm{\pi }}{6}$

Two periodic waves of intensities $I_1 and I_2$ pass through a region at the same time in the same direction. The sum of the maximum and  minimum intensities is :

(1) $I_1+I_2$

(2) ${\left(\sqrt{I_1}+\sqrt{I_2}\right)}^2$

(3)${\left(\sqrt{I_1}-\sqrt{I_2}\right)}^2$

(4) $2 \left(I_1+I_2\right)$