As, we known that the frequencies of sound waves lie between 20 Hz to 20 KHz so, their wavelength range between 15 m to 15 mm the diffraction occurs, if the wavelength of waves is nearly equal to slit width.
As, the wave length of light waves is \(7000\times { 10 }^{ -10 }\)m to \(4000\times { 10 }^{ -10 } \ m,\) the slit width is very near to the wavelength of sound waves is more evident in daily life than that of light waves.

If the source of light used in Young's double slit experiment is changed from red to violet, then their consecutive fringes will come closer.

While moving a car, there are periodic interruption in radio signals that we hear.It occurs on account of interfering of the radio waves, i.e a common form of interference called multi path interference.

No,it is because in lens maker's formula,
\(\frac { 1 }{ v } -\frac { 1 }{ u } =(\mu -1)(\frac { 1 }{ R_{ 1 } } -\frac { 1 }{ R_{ 2 } } )\)
\(\ =-(\mu -1)(\frac { 1 }{ R_{ 1 } } -\frac { 1 }{ R_{ 2 } } )\)
on reversing the lens values and signs get reversed.

As the refractive lens index for red is less than that for blue light and a lens will be bent towards the axis for blue light as compared to red
\( (\frac { 1 }{ f } =(n_{ 21 }-1)\frac { 1 }{ R_{ 1 } } -\frac { 1 }{ R_{ 2 } } ,\ f_{ b }\)
focal length of blue light will be smaller than that of red.