This video lecture from Waves (F.Sc. first year physics) This video explains the Doppler,s effect and one of its cases when obsever is moving towards the stationary source. and you will learn that their is change in speed but wavelength remains same. Find more e-learning material and educational video lectures in Urdu at maktab.pk. These videos are free to use for promotional and commercial purpose by keeping the credits to Maktab.