# Thought provoking problems on Waves

These problems are from pre-test conducted in teacher's workshops by Prof HC Verma and his team.

1. (a) A wave of wavelength $\lambda$ falls on an obstacle of linear size $10\lambda$. Will it show significant diffraction effect?
(b) A sound wave of frequency 500 Hz falls obliquely on a square card board of edge 10 cm. Will it show significant diffraction effect or it will mostly reflect accordingly to the law of reflection? Take the speed of sound as 350 m/s.
2. A ship is going on water when the sailor finds a fault which endangers explosion. He jumps from the ship and swims underwater away from the ship. He hears the explosion sound and then comes out of water and again hears the explosion sound. Explain how he can hear two sounds of one explosion.
3. The interference pattern on the screen due to a double slit is shown below.
1. Draw a diagram showing a possible set up to produce such fringe pattern.
2. If you were to blow smoke into the space between the slits and the screen, will you see the interference fringes everywhere between slits and the screen or no interference fringes in this region?