I list the question one by one. I hope this is a good arrangment. 1.The blades of a fan is rotating in an anti-clockwise direction. Its motion is frozen with a strobe frquency of 1000 Hz without a change in appearance. Which of the following is not a possible rate at which the wheel is rotating? There are six slits on the fan. A.200 revolution per second. B.500 rev. per second. C.2000 revolution per second. 2.Why the wavelength of a wave increase when it passes from a shallow region to a deep region? Does the amplitude change? 3.Why the wavelength of a wave increase when it passes from a shallow region to a deep region? Does the amplitude change? 4. Why does the wavelength of a wave play a very important role in diffraction? If the wavelength is bigger than the hole passing through, a very circular wave is produced while a very straight wave is produced if the hole is big enough?