58. Rainbow is formed due to a combination of ?

35. The radius of curvature of a thin plano convex lens is 10 cm (of curved surface) and the refractive index is 1.5 . If the plane surface is silvered, then it behaves like a concave mirror of focal length ?

18. The reddish appearance of the sun at sunrise and sunset is due to ?

17. An air bubble in a glass slab (μ = 1.5) is 5 cm deep when viewed from one face and 2 cm deep when viewed from the opposite face. The thickness of the slab is ?

3. A person is six feet tall. How tall must a vertical mirror be if he is able to see his entire length ?

A capacitor is charged to store an energy U. The charging battery is disconnected. An identical capacitor is now connected to the first capacitor in parallel. The energy in each of the capacitor is ?

A charge Q is placed at the comer of a cube. The electric flux through all the six faces of the cube is ?

A semi-circular arc of radius ’ a ’ is charged uniformly and the charge per unit length is λ. The electric field at the centre of this arc is ?

A 3 kg ball strikes a heavy rigid wall with a speed of 10 m/s at an angle of 60◦. It gets reflected with the same speed and angle as shown here. If the ball is in contact with the wall for 0.20 s, what is the average force exerted on the ball by the wall?