Due to Doppler's effect the shift in wavelength observed is $$0.1 \mathop A\limits^o$$ for a star producing wavelength $$6000 \mathop A\limits^o$$. Velocity of recession of the star will be
An electron is moving with an initial velocity $$\mathbf{v}=v_0 \hat{\mathbf{i}}$$ and is in a uniform magnetic field $$\mathbf{B}=B_0 \hat{\mathbf{j}}$$. Then its de-Broglie wavelength
Light of certain frequency and intensity incident on a photosensitive material causes photoelectric effect. If both the frequency and intensity are doubled, the photoelectric saturation current becomes
A certain charge $$2 Q$$ is divided at first into two parts $$q_1$$ and $$q_2$$. Later the charges are placed at a certain distance. If the force of interaction between two chagrges is maximum then $$\frac{Q}{q_1}$$ is