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

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